I\'m a hardcore
Grower, and before my journey into PE, and I would shrink and turtle at any time and any place.
PMMA doesn\'t necessarily stop your penises tendency to turtle, but it will definitely prevent how small it can get. The collagen will act almost as an implant and now when I turtle, it\'s not anywhere as bad as it used to be. I\'d note it as a significant improvement in that department.
I should note, however, when I do turtle/shrink, I get a sort of pig-in-the-blanket effect, which for some may not be a desirable look. I personally don\'t care.