Many years ago people were posting that the reason that the Stainless bolts corroded is that they were oxygen starved due to being buried in the glass.
I have hull #130 and I took out the plates, knees and all with a right angle grinder, built new knees with teak, reused the same plates and glassed over just like original to the hull and it's fine 15 years later.?
My boat is right near chainplate express. He is the the guy I used to fix the centerboard. But my chainplates are still enclosed in fiber glass. I have been thinking of opening them up. A can of worms perhaps