As you said, you won't get the energy required to propell yourself at this slope angle and speed. The terrain, because of its relative low degree angle and flatness, won't give you a lot of imput for your skiing at this speed.
Basically everything your body and skis do is determined by your muscles and not terrain induced.
This means that in order to accomplish the cross-under you need to actively lift/flex your legs to release.
I would agree with others above and choose a straighter stance with more vertical amplitude and a poleplant to ski short turns on this run.
Weighting or pressuring the outside ski more will make it bend more, hence reduce the turn radius of that ski and prevent the diverging ski's phenomenon.
Ski's diverge because the inside ski ski's a shorter radius than the outside ski.
I think your conscious choice for the crossunder on this terrain leads you to a low position and without terrain feedback that puts you a little in the backseat. Then again, Bode is always in the backseat.
I like your skiing though.
We should go out together sometime!