I would put 0 stock into what 'coach' @TomJ tries to state as fact especially when it comes to insulin.
'Coach' confuses short and long lasting insulin as he has shown recently in a thread here and he doesn't even realize when he is injecting insulin (true story, a few hours after he injected he realized his fuck up and panicked). He thought it was a cool story. For these reasons, IMO, no one should take insulin advice from 'coach' Tom.
IMO, 10 IU is standard or at least not considered a high dose for competitors and muscle monsters like you and several others on this board.
I don't compete anymore, I am in my 40s and I don't have the same goals/cuts/size as some of the beasts in this joint so for me 10 IU is a lot but considering the level of many in here, my opinion on a high GH dose is in the minority.
As far as whether or not someone will lose gains cutting dose in half, I have no idea. IMO maybe someone will lose gains but it won't have near the negative effect as cutting test dose in half.