Hello all,
I recently acquired Hull #185 (TAR33185M79F) in San Francisco. It's generally in good condition (despite not being used for three years); the L30 is frozen.

My main concern is corrosion on the chain plates. It consists of pitting around the bolts (stainless bolts, aluminum plates) and is perhaps 1/8" deep in the worst locations. Are there T-Ten chain plate/mast horror stories I should be aware of? Everything else appears pretty solid so I think I can sail until they are replaced (soon).

Second, does the shroud conversion upgrade from Tops-In Quality include new chain plates? If not, it seems smarter (from a corrosion standpoint) to use stainless for plate material - any thoughts on this?

If you have any doubts about the structural integrity of the chainplates, then work out a solution. I've used 1/4" Aluminum doublers on my other boat, where the problem was in plywood that rotted when water leaked in. You can buy aluminum plate online, most likely. Make sure whatever metals you use are the best galvanic combination. Pay extra for good stainless and the right aluminum alloy. I'm not sure what's "in" the fiberglass part, so inspect when you get the bolts off/out. I believe a high percentage of the T-10s actively sailing are on the Great Lakes, so corrosion would be less of an issue for us. We also have the advantage of having to pull the boats out of the water for the winter, which gives us ample time to put the rig down and inspect!

I only read about 'horror stories' but as I understand them, the problem was not the material, or corrosion, but the fiberglass bonding of the chainplate assemblies to the hull in a few boats. I have seen one T-10 still sailing and having hull distortion there. So I would think that if the fiberglass bond is still good on your boat, you might want to not mess with it if you can help it.

The TIQ conversion puts stainless chainplates on deck, but keeps the below deck turnbuckles, attaching the new chainplates to the old chainplates. I suppose there's less load on the below deck chainplates because there's more of a unitary structure, but they're still an important part of the structure. It's a worthwhile upgrade to keep water from leaking down below, which probably didn't help your corrosion situation in the first place. It does not include replacement for aluminum plates (although I had a rigger install it, so I haven't actually seen what's in the box!).