All of these (besides pinching) sound like horrible ideas. Yes, you will destroy your engine if you try using a hose clamp, but they now make special rings designed to do it evenly. There is a thread around here where a guy used a tool holder, and it seems to work perfectly. Doing ANYTHING to the piston is not necessary, and will not last. The sleeve is tapered, no pinch means this taper is gone... squishing the top of the piston isn't going to bring that taper back.