..I'd use that technique to seal those seams on the inside. I would consider cleaning the sides of paint and such and fiberglassing the outsides of the seams with fiberglass tape and epoxy.

That really is fairly simple and will work well. If there is a chine on the outside of the hull, fillet where it meets the hull instead. If the chine is inside, same same. Boat must be dry, paint cleaned off best you can.

http://www.epoxymethods.com/filleting.htm