You can create a nice fulcrum effect with this stretch by adding this simple variation:
— Grab towards the glans with an overhand OK grip (thumb on underside).
— Grab around base with an underhand OK grip (fingers on underside).
— Now, just twist the hand that’s gripping your glans downward, so your shaft bends around the nuckles of the hand that’s gripping the base.
The thumb underneath plays the fulcrum. The leverage is intensified as the thumb rolls over the top of your nuckles.
It might take some practice and changes to the position of your glans-holding hand, but I get a very good stretch to the topside of my shaft doing this stretch. You can also create same fulcrum effect bending right and left.
There’s a way to hit to do something similar and target the underside too, but I can’t describe it without dropping trou here in the office and getting hit with an harrassment suit.