those shoot throughs seem to be common to have issues with. one girl in my DDs class has everything beautiful that they are supposed to have except the shoot through. she even is super close to her mill circle and front hip circle. and she does everything so beautifully. she just can't get that shoot through. they have to have that alone to move to team, but i can't imagine them holding her back from moving because of that (at least it would shock me, since she is so amazing otherwise).
my DD for some reason got it right away and only struggles with it when she is really tired. she isn't close to having her front hip or mill circle though. and she has to have that with a spot to move to team.
we have a pullup bar, but it is too high for DD to practice much on. (i did this on purpose, LOL). she loves it.

got ours at walmart for 11.95.