Waterproofing?

The original boats had silicone wiped all along the glue seam. On Hobie 16s we now pour a resin bead to seep into and seal the lips. That would work on older boats if you clean out all of the old silicone. Otherwise… 5200, as mentioned already, is great stuff. You could do a “soapy-water bubble” leak test to see if there is even a reason to seal the lip.

Yep, be sure there are shroud reinforcement plates, but there are no more free upgrades for shroud plates on boats that old.