thanks
try to do what i did in this video on that one 180 dunk... when you drive to the basket carry the ball in the one hand while in gather and jump like you're gonna dunk one handed (but with that 180 turn) and just the moment before the leap off grab the ball with the other hand too,so you should have bigger momentum because you had one hand free while you were in gather,and a bigger momentum mean bigger vertical
and another tip,don't try to hold the ball away from the body before jump. when you jump,then you put/swing the ball away from you(you put it above head obviously
),and it's inertia should bring you upwards a little bit,too.
hope i helped.
regards