Hey all

I recently got myself a new ski (67" Obrien Allegiance) with Bio High Wrap Bindings.  So far so good, except that the bindings are pretty loose around my heel.  They tighten up well on the front of the foot, and are snug around my ankle, but i can move my heel side to side, quite a bit.  Any suggestions on how to fix this?  I feel like I'd have a lot more control without my heel moving so much.  Anyone else having a similar problem? 
Thanks
T