Instead of a reflector, I'd suggest a scrim, a translucent fabric that will
put the subject is a soft diffused light that is only one stop or so off
from the full sun, so you have a shade like space that is brighter than
shade.  This means that when you expose for the subject the background
doesn't wash out, just gets a step lighter, so you can print without a lot
of burning etc, you can use machine prints at a lab without loosing your
background or having the subject go dark.

A lot of photogs use a "california" scrim (which is actually made in
Germany) and has to thick handles for an assistant to hang on to, or to
clamp to a heavy duty light stand with counter weights and all.

I like a Larson 3x6 reflectosol, this is the large square/rectangle
reflector maker that opens from the center like an umbrella.   The main
advantage is  that with the center shaft (that bends on a pivot near the
head) an assistant, even an impromptu assistant like the model's boyfriend,
or one of the grooms'men, can easily hold it near horizontal over the couple
or even a small family huddled together and can control it in a slight
breeze.

also, you can make scrims and reflectors, there are simple plans availabe to
make them out of pvc pipe and sports nylon, and you can even buy the silver
reflector cloth they make reflectos out of, or you can get some mylar
'bubble wrap' insulation material that is decent for reflector use,
(sometimes you can find sheets of styrofoam insulation panelling to use, 4x8
foot, two inches thick, you can jam a stick into it to prop it up, 12 bucks
here stateside (probably 50 bucks on the island)

in the files section of the z-prophoto mailing list at yahoogroups.com you
can find an authorized scan of Dean Collins' Tinker Tube book (long out of
print) where he shows how to build a whole studio's worth of lighting gear
out of pvc pipe.

I think that using a reflector in the sun is the wrong way to use it, it
becomes like a spot light, a very harsh light.  you might as well use a
flash for fill, (or use a slaved key light on a stand and a high shutter
speed so the background drops down a tone, get a deep blue sky that way)
besides a reflector in the sun bouncing in the eyes is blinding, literally.

What a reflector is best at is when you don't think you really need it at
all, remember with film, what you see isn't exactly what you get, so when
you have the model in a nice open shade, a real 'sweet' light, that penumbra
at the edge of the shade, just before the full sun, take a step back, just
before full flat shade, there is that sweet spot where the skin glows, the
eyes sparkle, the subject is a stop brighter than the full shade, there is a
slight directionality, she looks perfect.  this is where a reflector can
come in on the shadow side and give that side a kiss of light so when the
film adds a bit of contrast, it all comes together perfectly.