I do same as Robert, if you have tapers, they naturally move toward the thicker end of the lam. I bevel my little block so the end is close to right angle to the lam stack.
The hole in form and zip tys would help too but havent tried it yet. Sucks when the stack moves either way from the desired point.
I know one guy who puts a pin on the other end(tip) to hold from going that way. Guess if you did both and cut lams and glass to fit between you would have em surrounded. Even cut 1/8 short so no binding wouldnt be bad.
Or heck a slotted stop with a screw would work on tip end. :D