Replying to Underrotating backflips>over rotateing

the few backys i crashed on when i was first learning them i would throw wayy to hard and overrotate to the point i would land flat on my back, wich would knock the wind out of me and i always thought i broke my back (i never did though) i also slightly underrotated a few and it never hurt as bad and was actually fun afew times. I learned dub backs on waterramps this summer so im gona be trying a few on snow this season. so ns whats your thoughts on overor underrotateing backys/ dubbacks?