A Capt Jacobson of an Aust Airline has mathematically (sine, cos, tan etc)worked out an equation to give you the exact height at which to flare. It takes all the guess work out of when to round out and flare.
Ace on Base correct me if I'm wrong but you hold a constant angle of approach using runway aspect not a constant aiming point. As your touchdown point passes under the nose cowling (as you are looking forward) that is the time at which to close the throttle and flare. According to my ATO it is approx 100 feet for most light aircraft (C152, 172, 182). No rounding out and hoping it doesn't float. It supposedly works every time and for all types of landings (flapless, glide, short field).
I can understand the mathematical concept but it is the explaining and teaching, having taught the aiming point technique for so long, that I am curious as to how others teach it.