A lot depends on the lightness/darkness of the things in the photo.  A
black vignetter essentially burns in the edges/corners making them
darker.  A white one does the opposite.  A translucent one sort of
smears those areas.  Which to use depends on what you want to achieve.
Skin color is unimportant.

If the hole is too big (any or all)...
1. Make another
2. Move it farther away from the lens
3. Use a shorter focal length lens
4. Use a smaller aperture (careful, makes the vignetter edges sharper
as does a shorter lens)

Is this a fade to dark type ND, layered screen or jagged edge opaque type
vignette?  Or a fade to white, wash out the corners type?

Back when I shot with a medium format camera and only used fixed focal
lenses, I used one of those bellowshades which had a slot way out away from
the lens, and the rule was to place the vignette at a distance equal to the
focal length.

A big variable is the f/stop.

Using such a vignette is difficult with a zoom.

I tried to use a highkey vignette but modern tastes don't flow that way.

Dark vignettes are great because they give a larger space to crop to various
formattes without sacrificing shoulders or composition.  Better yet, since
the average adult subject and far too many of the youth are way overweight,
vignetting a half length with a fade to black corners means you can keep the
hands but hide the big butts, or fade out the waist lines etc.

Vignettes made with screens can cause problems as specular highlights can
pick up that pattern, think about sequins on a wedding dress getting weird.

With digital its simple enough to do an action that will let you vignette
per image.

with modest sized images I'll do an oval marquee with a 250 pixel feather
and drag it from corner to corner, move it to center the composition, invert
the selection and make a new layer via copy, change the brightness/contrast
down 30 points or as needed.   With larger files I'll make a larger canvas
on a second layer (not background) with a soft erased center, then I'll drag
that layer over to each image, I make it a bigger canvas so I can center as
needed.

I just bought another lindahl bellows, I want to get some long bolts and
reverse the washer/nuts that hold the bolts to the standards, so the outer
piece is the solid end and the bolts slide through the part that clamps to
the lens filter ring, this will allow me to move the vignette in and out
without leaving the bolt rails way out front of the lens, I mean you can't
use a lens with any wide angle ability without getting the dang studs in the
image.    I'll have to figure out some kind of bushing that will let the
rails slide easy when I want them, but firm enough to hold so it doesn't
slip and slide.