I have done some clamping in the past. Today, however, I feel that my penis is much more sensitive to that type of pressure. I remember clamping for extended periods (about ten minutes or so) with maximum expansion and very little discomfort. Now I can’t even get a squishy erection without feeling too much discomfort. Perhaps my penis was in much better shape at the time. It’s been awhile for me since I’ve really given PE the same attention I’ve been giving it recently.
I guess I’d suggest working your way into it. I know from experience that I once could handle it and that now I cannot. I believe that if I worked into it again that I’d probably be able to do it comfortably.