The chainplates for the backstays on my previous boat, a Whitby built Alberg 37 were also glassed in. I did not like this at all because you really can't inspect them. The were bolted to a mahogany knee that was then encapselated in glass.

I had the pulled out and then glassed in new knees for the chainplates. We then changed the orientation of the chainplated 90 degrees and through bolted them to the knees with the bolts running fore and aft. It worked well and was not too costly. The work was done by a local shop in the Seabrook area.