I cracked a screen once ( Toyota Corolla ) when I shut the drivers door...didn't have any damage/chips previously done and it wasn't slammed shut either.
Also saw a bloke shatter a non laminate screen in a HQ once when he threw hot water on a frosty screen.Both the shattered glass and the hot water literally fell through onto the front seat of the car!!Wasn't me thank god.... I was driving past when it happened!!
Temperature variations ( even slow variations ) seem to upset screens as well as momentary pressure variations ( as told to me by a windscreen fitter ) can crack an otherwise good screen ie:- all vents closed in a car and door is slammed creating a momentary air pressure increase.Theory probably only really applies to newer cars though as our old cars aren't really that well draught proofed.
Perhaps body flexing during rebuild can put the windscreen fitting area of the body a poofteenth of an inch out enough to make a difficult fitment and subsequent tension on the screen??
I'm no expert on panelbeating/body repair procedures but it's just something I thought of that may explain a good screen cracking.
Will be looking forward to seeing this car at the nationals Malcolm whether the box is working OK then or not.... no one will be laughing at it that's for sure....... alternatively,look for an old grey FB.... thats mine..... they'll all be laughing at that!!
( if it gets there 
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