Uncircumcised stretching grip - glans problem

Hello peepee pullers.

I am currently on a routine which involves 20-30 minutes of inverted V stretches.
So I have to grip under my glans, stretch my penis over a cylinder and downwards.
The only problem is that I am uncut, so no matter how hard I grip, when I pull even with moderate force, my hand will reach the glans and I have to partially grip the glans for the stretch.
I wrap a cotton band about 1 inch under my glans and all over my glans.
But after I hold the stretch for 2-3 minutes, the tip of the glans is a little "deformed", and more purple. 5 seconds helicopter shake and the color is completely normal and I can still see some marks on the glans, from the wrap.
My question is: even if the glans looks normal at the end of the workout (maybe a little dehydrated), am I doing something wrong?
Can I cause slow but unhealthy damage in the glans?
Any suggestions on how I can perform this stretch more efficiently?
I am considering circumcision anyway…