"lowering your butt to your heels then pressing with your legs as you go up" is good for ramps without vert, usually small ones, where the last tangent doesn't reach vert: you have to push a bit in order to land inside the ramp (not on the plateform).
On verts, as you go up, you have to lock your knees a bit bent (and not push). Like this, your gravity center follow the good trajectory and you land knees bent, ready to push as you go down. If you push the way up on vert, you will do like Jack Brown, a mega flat landing.....
I will try to extract a pict sequence from vidz on verts/not verts to compare (something like this one).
: I was watching UR videos. :-D Hey, think I understand pumping more. Seems like the best way to think about it is lowering your butt to your heels then pressing with your legs as you go up? Thats right correct? Cause I'm keeping my butt up high in the air and mostly just leaning forward right now and just using upper body so I dont have to bend my knees much lol.....looks dumb too. But if I worked on doing tons of squats at home, think that would help get my legs strong again so I do it right.