Now that I'm training with a combined-training coach instead of a hunter-jumper coach, my seat is much deeper and further back. You won't see any daylight under my seat over a jump - I'm clearing the saddle but just barely.
I fall off less now < g > but part of that is because I'm pushing 50 (hard!) and I don't bounce as well as I used to.
Falling off less is the direct result of staying on more, and you just can't beat that! :-)