Bummer martin
I know we mentioned the cap (and the subsequent supporting 2x4s) keeping the hull from sagging/warping, but at the rate you were moving, I figured you'd have the keel back in in a weekend...
I haven't dug that deep but I'm certain this will be a lesson for many of us. I'm far from an expert but, yeah, me thinks the keel, the stringers and the cap are more structurally significant than cored sides. Get a keel back in lest she develop a hook or some other malady. Master Moesly and Co ran the heck out of his design and I've never heard that he cored the hull to make SeaCrafts stout and run true. He put the mass where it was most needed as I'm sure you saw by the amount of resin around that keel.
Good luck, I'm sure you'll set her straight.