: Well, the epoxy was hard and I was anxious to move on to the deck, since it's
: important not to leave the insides unglassed for too long. I learned
: something, (usually means an Oh Darn, but this wasn't too bad! ). I
: carefully unscrewed the uprights from one of the forms....CLUNK! The form
: dropped out....hmmmm. Of course! I had used staples and since they were
: all gone, there was nothing to hold the forms in the hull. Sure enough,
: CLUNK, CLUNK, CLUNK, they all fell out as I unscrewed them.

I faced the same problem and just to keep the forms square, I cut 2x2 braces between each form and screwed them in to hold everything together.
Good Luck