The more you practice the higher you will go in smaller chop. Your body cashes the checks. The point is safety first. Wear a helmet when you are first trying to loop, it will save you in the end. Once you hit your first loop you will be kicking yourself that you haven't tried sooner.
Speed is more important at first than height.
You need speed to get the rotation going. At first it will be more of a roll across the water than an endo-loop. Equipment and body breakage is not as bad as you might imagine. BUT safety is always a priority when learning. Funny, but an element of truth.