Most conventional fixer formulas can be converted to
"rapid" fixer by replacing the Sodium Thiosulfate with
Ammonium Thiosulfate in the correct amount.
  The simplest fixer formula is just the thiosulfate and
Sodium Sulfide. 5 grams per liter of Sulfide is enough to
protect the Thiosulfate but some additional will prevent
staining by carried over developer, around 15 grams per
liter.
  There two reasons for making a fixing bath acid: one is
for the hardener, alum hardener works only when acid; the
other reason is to prevent carried over developer from being
active. If a plain water stop bath is used with a neutral or
alkaline fixer it must be thorough enough to wash out the
developer. However, if there is enough sulfite in the fixing
bath it will prevent carried over developer from causing
staining although it will continue to develop just a little.
  Fixing time for either film or paper depends partly on
the nature of the emulsion and varies with any kind of
fixer. Rapid fixer _at film strength_ fixes paper fairly
quickly but the time varies from around 30 seconds for some
types to over a minute for others. The only way to test for
this is to fix samples for varying times and test them for
residual silver halide. The standard tests are either a 1%
solution of Sodium Sulfide or a 1:9 dilution of Kodak Rapid
Selenium Toner. The toner test works only if the emulsion
has been well washed. Instructions for making up the Sulfite
test can be found in several Kodak publications but I am not
sure its on Kodak's web site anywhere. The test solutions
"tone" any residual halide just as they would image silver.
If the prints or films are completely fixed the test
solution will not produce a stain. Any yellow or brown stain
indicates incomplete fixing.
  There is a lot of misunderstanding about wash times.
Neither Sodium or Ammonium fixer has any advantage this way.
In a normal acid fixer with white alum hardener washing
times are extended because two conditions tend to bind the
thiosulfate and the reaction products of fixing to the
emulsion. One factor is the alum hardener. Alum tends to act
like a mordant when in an acid environment binding the
thiosulfate rather tightly to the emulsion. The other factor
is pH. Photographic gelatin has a "natural" pH, or
Isoelectric point, just on the acid side of neutral. When
acid it tends to bind thiosulfate because of the electric
charges of the atoms. When made neutral this binding force
is eliminated and the gelatin tends to repel the Thiosulfate
ions and also the Thiosulfate complexes that result from
fixing. At neutral pH alum hardener still functions as a
hardener. The electric charge binding can be eliminated by
making the emulsion alkaline but the hardening action of the
alum is destroyed.
  A plain Thiosulfate and Sulfite fixer is about neutral,
additional alkali really is not necessary.
  Wash times for fixer which is neutral and has no alum
hardener in it are about half those for hardening acid
fixer. Note that thiosulfate is bound up in the support of
fiber base paper by other forces, notably frictional forces.
The nature of the fixing bath does not affect this a lot so
fiber paper still needs long wash times compared to RC or
film.
  The use of a neutral Sulfite wash aid, like Kodak Hypo
Clearing Agent, will change the pH of film or paper to
neutral and also has the property of displacing Thiosulfate
ions and fixer reaction products by an ion-exchange
function. When a sulfite wash aid is used wash times are
considerably shortened even when an alkaline fixer is used.
Film washes out in 5 minutes, double weight fiber paper in
about 20 minutes. The wash aid will also dislodge some
reaction products of incomplete fixing which otherwise do
not wash out even in very extended washes.
  Ammonium fixing baths do have some Ammonia odor. The
neutral fixers have less than acid fixers but it is still
there. These fumes are NOT dangerous but may be irritating
for some people. I don't know of a solution for this. Acid
fixing baths of all types tend to evolve some Sulfur Dioxide
gas, this is the "sharp" odor associated with fixing baths.
It can be very irritating to some people and can set off
Asthma, etc. Neutral or alkaline baths produce much less of
this gas than acid baths.
  There are a number of ready mixed neutral or alkaline
fixing baths on the market. They are used in color
processing and are also sold separately. Some fixers are
sold with the hardener in a separate container which can be
added or left out at will. Kodak Rapid Liquid Fixer and
Hardener comes this way. The hardener bottle also has
additional acid in it. Without the hardener this fixer is
still acid but less so and has less odor.
  To insure complete fixing a two bath system is
recommended, especially for Sodium Thiosulfate fixer. One
begins with two fresh fixing baths and fixes for half the
time in each. The second bath remains relatively fresh and
can complete the chain of reactions necessary to make all
the unused Silver Halide in the emulsion soluble so it
washes out. The capacity of a single fixing bath to do this
is very limited, a two bath system has on the order of ten
times the capacity of a single bath.
  BTW, because RC paper has a very thin emulsion it washes
out completely in about 4 minutes even when using an acid
hardening fixer. The use of a wash aid is not necessary.
  I hope this is helpful.

Just use Rapid Fixer with hardener. Forget all this nonsense.

(Details snipped.) FWIW, the formula you posted is Ryuji Suzuki's
creation; its Web page is:

http://wiki.silvergrain.org/wiki/index.php/Fixer

I mention this because it's not clear if you got it from there or from
some other source with less information.

The extent of the ammonia odor varies from one formula to another; with
some, it's pretty strong, but for others it's barely noticeable. I don't
know about Suzuki's Neutral Rapid Fixer, since I've never used it. I have
used a commercial variant, Silvergrain Clearfix Alkaline
(http://www.digitaltruth.com/store/silvergrain-fixandwash.html). It has a
very subdued ammonia odor; however, it's not identical to the posted
formula. The two might vary in the strength of their ammonia odors.

This formula is published in Anchell's _Darkroom Cookbook, 2nd Edition_
(formula #134). Anchell specifies a 10-minute fixing time for prints, so
this doesn't qualify as a rapid fixer in my opinion. This isn't
surprising, since rapid fixers are usually made using ammonium thiosulfate
rather than sodium thiosulfate.

FWIW, I've used the rapid variant of TF-2, known as TF-3. It's definitely
got a strong ammonia odor. Despite this fact, I've used it in trays. It
wasn't a pleasant experience, but it was actually less bothersome than
acid fixers, which irritate my nasal passages although they don't have as
strong an odor.

A commercial variant of TF-3, known as TF-4, is available. I've never used
TF-4, but it's supposed to have a less powerful odor. It's also pretty
inexpensive.

I've not used either of them. Personally, I hate sitting there fixing
prints for 10 minutes, so I use rapid fixers now, especially for prints.
In theory, it won't make any difference for the quality of your final
prints, assuming you use the products correctly. Thus, it's really a
question of personal preferences for things like your patience for long
fixing time, your tolerance of ammonia odor, your sensitivity to the
sulfur dioxide produced by acid fixers, etc. You may just need to try
multiple products to figure some of these things out; one person's
"overpowering ammonia odor" may be another person's "barely noticeable
ammonia odor" -- and similarly for other factors.

Correct. This shouldn't make much difference for most products. The
emulsions of Efke films are reportedly rather delicate and can benefit
from hardeners, but for most films and papers it shouldn't make much
difference.

As I mentioned, I've used TF-3 (http://www.jackspcs.com/tf3.htm) with
success, but it does have a strong ammonia odor. I've recently been using
Silvergrain Clearfix. It's got a much more subdued ammonia odor than TF-3
but is almost as fast-acting. Its Web site has unusually clear and
extensive instructions. On the downside, it's pricier than some products.
I'm thinking of giving TF-4 a try for this reason.

I've mixed my own fixers from time to time, but for the most part, IMHO
it's not worth the bother. Certain commercial products, such as TF-4 and
Kodak's Flexicolor (C-41) fixer, are actually less expensive than anything
you could mix up yourself, unless you find a good local source of the
sodium or ammonium thiosulfate. (Flexicolor fixer, despire being marketed
for color film, works fine with B&W film and paper, and has the advantage
of being very inexpensive. I don't know the exact fixing time for B&W
paper, though.)