i would say that if arrow weight affects your form than it is too heavy. i used to shoot over 700 grains with a 60# bamboo viper, but i found that to compensate for arrow drop - loss of trajectory - at 20 yards or more i had to raise my bow arm too much which threw my alignment off. i now shoot around 620 grains and my arrows have a much flatter trajectory, which feels right to me. the obvious question is, do you have a reason for increasing arrow weight - improved bow performance, better penetration, etc. - or do you just want heavier arrows?