grip question [are curved wrists okay?]

is it safe to let your wrist curve around the pole in certain spins or should it be straight? i've noticed that when i do some spins on static pole, i let my wrist bend like so: http://localhosthttp://img.photobucket.com/albums/v86/shymahr/grip1.jpg now i've got the confidence to try more stuff on spinny pole, i've noticed that kind of grip just isn't flying. i tried to do my spins with my wrist straight, like the next picture, because it feels more natural but it's much harder to hold on! http://localhosthttp://img.photobucket.com/albums/v86/shymahr/grip2.jpg both pictures are taken from me standing in the same place, just gripping differently. i'm explaining this terribly but hopefully someone understands what i'm getting at? for all i know, maybe i just struggle to do them properly 'cause i'm not strong enough but i'd rather check with folk that know. i'm self taught and trying not to get into bad habits but sometimes i don't realise/know i'm doing anything wrong - eek.