Here's a body position mental image that I stumbled upon many years ago when working with low jump number students on docking. I'm not a current instructor, and haven't been for many years, so maybe this is alreay part of the current curriculum. Anyway, for some this helped, for others it didn't. For many, using this mental imagry in combination with video really made the light go on.
When we're teaching students to move using legs, we tell them legs out to move forward, in to go back and neutral to fall straight. Then we put them on a creeper and practice and hopefully build some muscle memory. Then we jump, and for many it's a frustrating experience as they swear up and down that they had their legs out and couldn't go forward, or had their legs neutral and back slid. The problem for many of them, it occurred to me, is that the muscle memory we teach on the ground is not the same as the muscle action we use in the air. For example, to maintain a neutral leg position on the ground, we have to contract our hamstrings to fight gravity and keep our lower legs from falling to the floor. But in the air, we have to use the opposite muscles to keep our legs from being folded up behind us by the force of the relative wind. So when a student feels like he is extending his legs in the air, he may actually only be applying enough force to maintain a neutral position. Similarly, when he feels like he's holding a neutral position in the air, he may actually have his legs folded up behind him if he's not pushing against the wind.
Anyway, just thought I'd throw that out there. I've seen it help some who were having docking issues related to leg position.