I have a xG3 in P2. I haven’t done any cracks since getting it (don’t rock climb much these days) but just from sticking my hand in other places, I would say you definitely would not want to have one on the back of the hand.
P0 would be better, but may still provide some discomfort when jamming with a fist.
Again, I haven’t done any climbing with my implants, just educated guess having done it and having implants in P0 and P2.