This was a great illumination for me when your protégé Stephaney Fish Crossman instructed me a few months ago. My horse finally went forward with rhythm and for the 1st time I was able to keep my heels properly aligned.
you might be interested to know in Australia pretty much all pony club riders get told repeatedly and loudly to 'put your heels down'. An interesting effect occurs where by virtue of putting their heels down they ride on the base of their toes. Riding on the base of your toes (like a door hinge) makes for putting the heel down easier though makes balance much more difficult and they turn in water skiers gripping with their lower leg i..e., squeezing constantly, it's like the accelerator is stuck to the floor the horses are always running away. Subsequently I learnt foot placement is really important for developing and refining balance. On the weight in your foot, particularly for jumping I tend to teach let the weight fall through your feet in trotting, not push down, same as when sitting, just let the weight fall through your seat bones. I actually like a 50/50 weight feel across my feet and seat when cantering. it's very important to be able to take the weight across the bar of your foot in the stirrups for jumping. Being able to take the weight across the bar of your foot gives you balance, flexibility and elasticity in your movement, it's same principal as in Latin dancing funnily enough, you can't dance flat footed on your heels.