I have had sex before while heavily clamped, like you said it goes so hard, like 120% erect and veiny as hell! I would just say watch your penis for cold/numb feeling going dark in colour, try and do it with the clamp for no more than you would do a clamp set, 15-20min max!
DLD to answer, what would she say- my misses loved it to start with, but after about 5min she didn't like it, she said it felt to big!
brit