I've got a few ideas for modifications/replacement of the clamps, just haven't had the time to get started on them.
One quick way to make sure the cant is square to the blade is to draw a line across the cant with a framing square once the opening cut and the 180 cut are made. It works for me.
I've also noticed clamping too tight causes the problem. Once I have a square edge, I have been guilty of not clamping at all, just letting the bunk stops keep the cant in place.
Stew