I've never used one, but I've always heard that the penis head is different from the shaft, in that it can't be permanently changed through any kind of PE. When I finish a pumping session the head is always bigger, but it's the first thing to return to normal size, and while I think I've gained a little permanent girth increase, I don't think the head has changed at all. Anyway, that's as much as I know. Hopefully someone more informed than me will chime in soon.