I once removed/replaced the glassed-in chains on a buddies boat. a real head
scratcher til we realized they where T-shaped at the bottom. tons of gritty and dusty work, lots of cabinetry demo, all in all a miserable job. we replaced them with externals. that was 20 years ago.
today I wouldn't hesitate to replace with composite chainplates. if you've got the demo done then most of the "prep" work will also be done. composite chains eliminate corrosion
concerns, eliminate deck leaks
, aren't terribly difficult to fab up, can be hugely over built for little extra money
(safety factors of 10 or more) and do a better job of distributing load paths. for me, the last thing I want on my mind when the weather
turns is whats holding up the stick.
of course the universal caveat is you can do all the work yourself and take your time to do it right. if you've got to hire a composites fabricator to knock them out then you better have Larrys money