I found both 7 Or Better and A Bit Bigger a couple of years ago and I was overjoyed; they purported to be exactly what I had been looking for. I spent a considerable amount of time filling out my profiles, searching through and adding all the women I found attractive, and crafting hundreds of unique messages to them. The results were pretty underwhelming. As others have mentioned, almost all of the profiles were fake and/or abandoned long ago. Of the few women who replied, reverse image searches revealed most to be misrepresenting themselves. Never found anyone anywhere near close enough to meet, although I did share pictures and cam with a few ladies who suspiciously looked different in all their pictures or had perpetually broken cams. In the end I put more time into the endeavor than I would have on a regular dating site to get to a sexual relationship with nothing to show for it.
I tried Adult Friend Finder but found it pretty spammy and useless without a paid account.
I also tried out FetLife, thinking that a big cock is a pretty popular fetish, but found most people were looking for something kinkier (and not the most attractive userbase either).
So I never did arrange a date/hookup based on my endowment. It's more satisfying to get a date based on charm and appearance and have the size be a surprise when the time comes anyway, but it would be fun for one night. I think the concept behind a dating site that matches the well-endowed with the partners that seek it out makes a lot of sense and it still surprises me that no one has done it right. I'd imagine that the personal ad section of LPSG is the closest one out there.