Sure it's not an original idea, in fact, I may have seen it here on some build-along or another, but is it common practice to drill a hole in the butt end of your lams/wedge and "pin" them together prior to glue-up? Seems like that would take the worry out of the lams shifting when the pressure is applied. Side-to-side shifting would be taken care of by the form itself, if the width of the form matches the lams width. (2-piece, airhose form)
I haven't actually built anything myself, just thinking out loud and getting ready to order some supplies. I'm assuming you would normally have excess length on the butt end of the limbs to work with...