Grip while stretching... hurts the back of my head

I grip for doing the JAI routing or the DLD blaster (although I suck at keeping track of count and how long I kegel or reverse kegel). However, I cannot hold the stretch for more than say a minute because it starts to tingle/burn/hurt the back of my head (on my dick).

I try to soften the grip (I’ve tried the “A” grip, and the OK sign behind the head) but my dick just slowly is pulled through my hands from the tension I create in the stretch. I use powder for grip, but that dosen’t help. I’ve even tried using cotton cloth. No luck with that either.

How long can you hold a grip while applying stretching tension for before relaxing and re-stretching with the grip and tension?