The shot on the left represents my best attempt to come up so far. It does seem to help to try coming up after dropping back rather than starting from a UD, feet, legs, hips, chest, arms....all are in the right alignment, plus there's the muscle memory of where you were a few moments before.
Looking at the shot on the left I can see that I've managed to get my hips over my feet but that they are not as high as the shot on the right. The angle between my thighs and my calves is ever so slightly less on the right and I think it's that I need to aim at (look at how much of the corner of the radiator you can see behind me). If I forget about the top half of my body and focus on reducing that angle, of getting my hips a little higher and slightly further forward then it should carry me up.
In fact when I think of some of the dropback assists I've seen, the teacher has their hands on the hips lifting and drawing forward.