Good ideas, thanks Bushwacker! My main concern is screwing two things together with a major air gap in the middle. The screws won't really be "tight". You're right about them being sharp deep threads. On one, the hole size had expanded to basically the size of the screw head, and was loose before I started the repairs...actually both middle ones were loose. I'll be checking out the health of the threads before I drop the hatch in.
Still need to drill and countersink the holes back out:
