Definitely fix, repair or replace the rear hatch cover. Some light plywood,
a fibreglas kit, a bit of gelcoat and an lazy afternoon should do the job once
you've worked out the measurements and know what you want in the end.
I acquired my Mistral 16 simply because the previous owner didn't have
adequate flotation in the stern or a solid hatch cover locking system. When he
capsized the stern filled with water and the boat went stern down. The only
thing saving it from sinking completely was the foreward flotation. His mast got
dragged and broke and he got very discouraged. I now own a nice little sailboat
for a very low price and I got the pleasure of learning the boat from the
ground up so to speak because I did all the repairs myself. So, definitley
fix the hatch cover problem.
I also got a large inner tube, located it inside the stern hold cavity and
pumped it up tight. Then I locked down the hatch lugs and always check to ensure
everything is tight before I go sailing. I'd hate to get swamped by a following
sea and find there wasn't enough flotation to at least allow me to maintain some
leeway. Being blown ashore is hazardous to ones heallth and dignity.
Paul