Yes for sure I roll back the foreskin - would never get much of a grip otherwise. Maybe skin stretching can also be like a burn. Anyway I just re-tried it and think I got a good stretch - certainly can see what you mean by easing into it and getting that bit further.
On another note, I have read all the posts about straight wrists and body position so I understand the principle well, and I do manage to get a straight arm and enough force. I can use a straight wrist but then I end up using the thumb a lot more for holding the glans (and not sure that I can hold that grip as well), and also the glans starts to be pulled outwards away from direction of pull (seems this happens due to the wrist being straight). Am still experimenting but just don’t seem to be getting it right, so continuing with more of a horizontal wrist unfortunately.