Re: Restoring 1972 16' ss
one caveat about welding around seams on a tinnie that i learned the hard way: the pliobond or whatever the mfgr uses to seal at the seam tends to vaporize and contaminate the weld. don't think i'd weld that given where it is for that reason, totally aside from the issue of stress cracking later.
i'd start on that one by trying to get corner back into shape as best you can with a big dead blow hammer and a hunk of 2x4 or 4x4 made into a giant "drift". you'll probably have to pull splashwell and transom to do this. once you get it back as close as possible to correct contour, wire brush to down clean metal and remove all old caulk. slather gluvit or coat-it into the seam and around all rivets and on the entitre area and the dog and.....oops, got carried away there. i strongly suspect this will fix the leakage.
then you can look at whether you need to brace the area any. i kinda suspect not, altho it certainly never hurts. here's a thought: since gluvit is essentially an epoxy resin and sets up accordingly, what about using some glass cloth laid in with the gluvit, and maybe an extra coat or 2 of plain epoxy resin? wet it out properly and use fine mesh cloth and you should be able to get it to form into the corner nicely and even pretty tight on the rivets. they literally use this process to build entire boats from plywood, so i reckon it will work to strengthen a repair.