This is essentially jelqing while clamping, which sounds EXTREMELY dangerous. I will not be trying this exercise. But, I do hope for the best from those who do.
One comment on the exercise particulars. You say use an underhand (palm facing up) grip with both of the hands, one for clamping and one for jelqing. To me it would seem more effective if you used an overhand with the palm facing down. How can you possibly dig into your CS with an upward facing palm, your index finger would be on the top of your penis, rather than the bottom. I note that you said you can get deeper into the base with an underhand, but I can't understand how that's possible. With an overhand grip you have your other 3 fingers in the way, which limits how far you can press into your base, and especially limits your ability to exert pressure on your CS since you're unable to press as deep. If you used an overhand, you would be able to reach much further down the CS and trap much more blood. I will admit that it would make the additional jelq a bit more difficult though.
Anyway, just some commentary. I think it's perhaps too intense for most people. I would say, a 6 month period before trying these.
One comment on the exercise particulars. You say use an underhand (palm facing up) grip with both of the hands, one for clamping and one for jelqing. To me it would seem more effective if you used an overhand with the palm facing down. How can you possibly dig into your CS with an upward facing palm, your index finger would be on the top of your penis, rather than the bottom. I note that you said you can get deeper into the base with an underhand, but I can't understand how that's possible. With an overhand grip you have your other 3 fingers in the way, which limits how far you can press into your base, and especially limits your ability to exert pressure on your CS since you're unable to press as deep. If you used an overhand, you would be able to reach much further down the CS and trap much more blood. I will admit that it would make the additional jelq a bit more difficult though.
Anyway, just some commentary. I think it's perhaps too intense for most people. I would say, a 6 month period before trying these.

