On the advice of Glassdave, I've started using West System 404 adhesive filler mixed with VE. Stuff is tenacious! And there are zero incompatibility issues when glassing over with biax and VE, as VE is the base resin.

keep in mind when using epoxy that it relies 100% on mechanical bond. in other words any surface that has epoxy applied it needs to be 100% sanded or ground, not just cleaned over lightly by hand but thoroughly sanded/roughed up. the percentage of bond strength is directly proportional to prep.

I totally agree with Dave. You would not be able to "feel" any flex in 5200 although it has some elasticity. A light tabbing of glass with epoxy or whatever is just a bandaid and will not withstand repeated cycles of slamming. On my personal boats that I build, the deck and hull sides are one bonded laminate with four to six layers of lamination on the outside and on the inner side. They are not going to delaminate under most foreseeable conditions. Many manufacturers just do not laminate proper scantlings no matter what the designer specified. Limited tabbing will help, but in my experience 5200 will be superior if you do not have access and do not do stepped tabbing. I will let Dave weigh in on this. Good luck. Bob.

one of the problems with injecting epoxy into a blind void is you have no way of knowing it's condition and also no way of doing any sort of prep. For a standard marine shoe box joint I would have to agree 5200 is probably best if you cannot do a fully tabbed joint.

you also need to through bolt the hull,,use 3/4x3/4 ss box tube on the inside..each through hole about 6'' apart and the box tube 3'' in legnth..

my scarabIII was done like that except they used a piece of rubrail on the inside. was actually a pretty good idea and seemed to give it some good clamping force

Those are great suggestions. Maybe I'll just stop where I'm at for right now and enjoy the summer. Then over the winter redo the whole hull. And as always thanks for the input.

Are you saying to use the box tube like a big washer? or is there another reason to add box tube?

I'm assuming yes to use it as the washer. But, using the full length it will give it structure and rigidity along the length of the hull.

If this was directed at me (I don't mean that in a crappy way)....
I used the epoxy to fill the gap and bond the previous tab back to the hull. The poly was applied to the top side of the tab to the hull. So aside from some very small spots where the epoxy oozed out, the polyurethane resin / chop mat was bonded to existing polyester surface. I took it out into some pretty nasty stuff over the weekend and the repair looks good. However time will tell. Again, Aside from using the Six10 I don't think my repair was really much like the OP.