: Mick, you certainly have a knack for making even the simplest
: process seem complicated. Rube Goldberg would be proud of you!
: ;-)

Oh no! I like simplicity, I like simplicity:
I was trying to be helpful as well - I even gave an alternative that was even simpler to mitigate against the possibilities in my mind! And way simpler at the centre. Just a 'Rube' approach with no gold and certainly no bergs hiding anywhere, heh heh.

I love using wedges - because they are such a simple and flexible approach. But I use a moderate amount of setting force (as I thread them on the strong back with a sloppy fit so that I have allowance for form readjustment). On one build however, everytime I slackened off a wedged form for precision readjustment (wedge for each form), the whole assembly shifted out of whack about 1/16" near the centre. Every time. Very odd.

So I pulled everything apart and dismantled the plywood strongback - and found that the inner plies of the plywood on the jammed side piece only were corrupted in that one location.
I rebuilt the strongback with better material and it stayed true during adjustments. Sheesh!