I am currently in the middle of attaching my armor, and I've gotta say... the snaps are turning out great. They're very sturdy, strong, and they are capable of pulling the armor in pretty tight. I'm using Dritz 5/8" heavy duty snaps on 3mm Sintra. To pull the armor in close, I sanded out a recessed area (about halfway thru the Sintra) for each snap, then filled it with JB Weld. Pressed the snap into the weld and sanded out any areas around it.
The collar was a pain to line up, but the shoulders and chest pieces have been fairly easy. Highly recommend the recessed snaps (or bolts, they're pretty much the same IMHO after some testing on scrap)