My policy with the 3 girls before my 6 week old son, was to get the prefolds snug, to stop leaks as much as possible. I've noticed that when I angel wing fold, sometimes the hole of his foreskin is a little pulled back and more open. I assume from the rubbing of the diapers, this doesn't happen when he pees diaper-less (It goes back to completely covering everything on it's own by the next diaper change). This never happens with my fitteds or any other diapers. So I've resorted to using a really loose bikini twist fold, which does not affect the opening of his foreskin, but it's obviously not very good for containing messes.
Am I overreacting about having the diapers loose? Is this just what happens with uncirced babies? Im a little new to these baby parts :P