I"ve removed/changed the location of bulkheads that were bonded to the hull
with Polyester Resin. On one boat that had been molded less than 6 months before, the bonded area had been ground with a grinder and wiped down thoroughly with Acetone before the bulkhead was tabbed on. In short, know it was done right in the first place to relatively fresh laminate. When I ripped out the bulkhead(s), found the best way to do it was just to muscle it back and forth till the the tabbing with the hull
broke loose. Some bonds did have to be cut/ground off but it was a very low percentage of the bonds. On my current
boat with bonds that were done by the factory 40 years ago. It was pretty much the same thing, just rip the tabbing off the hull. Doesn't give me a lot of faith in repairs
made with polyester resin.
I don't see where using epoxy
resin vice polyester is going to create a stress riser. The strength in FRP construction comes from the fiberglass
strands in the matt, cloth, and roving. The resin basically just keeps the strands in place. A bond that doesn't hold well is a hell of a lot more of a problem than a join that may or may not be stronger than the surrounding structure.