RE: S-type 126 '07 foot strap positions
Once planing, are you lifting the windward rail, particularly with your front foot? You really want avoid sinking your windward rail, especially driving hard to windward. It's much slower, hurts your upwind potential and promotes the possibility of your heels catching.
However, if you have very large feet, you still might have problems, even if you're doing everything right with your board trim. If that is the case, your easiest solution could be moving the rear straps further inboard. But, before you try that, I would recommend experimenting a bit with your strap adjustment. Allowing more of your foot into strap could help some, but take care not to have the strap too tight, where it's difficult to get your foot out.