I've noticed a few changes after tucking regularly, without hormones or anything that should affect that area.
When I first started, getting each testicle "up there" was a bit of a challenge; I had to lie down to do it, and they would sort of "pop" into place and leave very slight bulges. Now, they seem smaller and slide easily in and out, sometimes on their own, leaving my front completely flat either way. Also, the skin around them used to be tough and coarse, but is now smooth and elastic.
Are any of these effects normal? I hadn't thought tucking 24/7 was unhealthy, and if shrinkage is all that's happening I don't mind it at all, but I don't want to cause myself harm or sabotage anything for any future surgeries...