yes, I had the vee-string by Castle Supplys and have posted on here about it when i first joined... they are NOT intended for long term use and would require hefty refitting by a skilled artist if that is your intention to wear them long term. The only one i bought in 2008 fell apart on me after less than a year's casual use. It is actually very thin (+/- 1-3 mm) latex in most places. It can hold the penis back, but not truly bind it like tape, pantyhose or shapewear will do for you. And the string is just that- a string. real bugger if any hairs get caught up in it, nevermind the chafing on the tailbone (same problem with slingshot type gaffs). The ones they use in the videos must have been enforced with the extra layers of latex that they sell separately. The size accommodation for the genital area was also much bigger than needed for me, so i can only assume that it was intended for those that are well endowed in girth.
There is another line called the FemSkin. It is a whole lot costlier being either a full bodysuit or a girdle. They are designed a whole lot better by being thicker for the vaginal area, but both are advertised as sex toys, and neither the fem nor the vee eliminates the bulge.
It looks like the other product you mentioned, the Pro-V, has expanded off of those designs to make a true prosthetic silicone line that isn't for the intention of intimacy. I looked at the site and video on the theultimateprostetic website. I would still have my concerns on hygiene wearing it for several days without cleaning, considering all the possible UT and/or yeast infections that could spring up in that time. But for the cost listed, the customer could almost reserve a surgery date in most places for that much...
I would also consider looking for a Gina Clip. Just found this item by accident on youtube looking up the Pro-V... and wow, it's method matches a whole lot to the inversion method i used for years once i found something that worked. definitely can't post the video directly, but you can find it on google search with the following term:
"Gina Clip on The Crowdfunding Center" the indiegogo page for the creator's attempt at expanding into the U.S. market.
WARNING! private viewing only as it shows an actual demo also has a chart that can be used to do the inversion method that i have talked about numerous times for smaller sized users. I have heard of some making their own versions of the clip using hardware supplies and a bit of improvisation.
In the long run, I found it more efficient to instead use the clothing items freely available at local stores instead of spending any more money on something that would be useless once i got to being post op.
Spanx is VERY good for this, as are the flexees line of shapewear from Maidenform. Each of these lines have varying degrees of binding, and a few have gussets for going #1 without need for removal in tight spaces. (that can be a bit haphazardly to do pre-op, but is very useful once +1 year post-op.) For me, what was tight in the crotch pre-op, ended up fitting perfectly now post-op, and I've had them for three years now.

you can also craft your own gaff/panties by recycling control top pantyhose and discarding the parts that had runs in them and using a wedgie like pull back to bind it in place. there are many examples to keyword search throughout google, youtube, and on here... there's always the tape tuck/invert methods too that I've successfully used for a string bikini at the beach and in the hot tub, but that is
not recommended for long term use due to likely irritation and rash from the bonding agents (even if it will hold form for several days)