I had the same problem with the new design Chainplate Covers on my MKII. A local machine shop milled the four covers down to 3/8-inch overall height. The charge was $48 for all four which I thought was very reasonable. They look good and still have sufficient height to provide the additional sealing surface.

I bought some of the chain plate covers from Catalina Direct. They are apparently not made by Catalina. I was pretty confused on how to install them because they did not fit going up.

I talked to Catalina tech support and they had no comments on the new covers, just that Catalina Direct is a dealer and sources through a lot of suppliers.

They indicated they had changed their designs to keep core materials several inches away from the chain plate cutouts. I had cut my new core back 3/4" and filled the gap with an epoxy mixed with a compression strengthening filler. They recommended then filling the cutout with 5200 when you inserted your chainplates back in, then installing the covers with 5200.

I bonded the new covers in coating both inside and out with 5200 and with the new flange facing down into the enlarged cutout. It works pretty well and there are now multiple layers of resin and 5200 protecting my core. If the chainplate does leak it will be down into the cabin and not the core. That's the theory anyway.

To (re)seal the chain plates, is 5200 still the best option?  If so, should we use the fast cure (red) or regular (blue) 5200?  A search here is all over the map with some suggestions many years old.  Just trying to obtain the latest thinking.  For the through hull fasteners, I probably will go with Maine Sail's recommendation for the butyl tape.  Any suggestions for cleaning, prep, and application are welcome as I plan to rebed the chain plates and the interior handrails this weekend.
Thank you.

I just had my chain plates out while doing a re rig. I chamfered the opening about 3/8 back from the chain plates then pushed in Butyl tape. put extra tape around to fill under cover plate and to squish up when tightened. Did this on our C30) and never had a leak. I would not use 5200.

Do the new Chainplate covers from Catalina Direct encompass the screw holes too (which is the suggested design) or does the Catalina Direct just cover the Chainplate flange opening?  I would like to purchase the "larger" Chainplate which was shown in the Forum that includes flange opening and screwholes.  Any suggestions where I can purchase these?  The 2012 Forum email doesn't work. Thanks.. 

How the heck are you going to rebed the chainplates in the future if you seal them with 5200?

There is NO place for 5200 on a boat!! Where's Larry Brandt?!

Search rebedding on this forum to learn a lot about sealants and their uses.

Catalina direct now warns you may have to grind down the cover to allow clearance for your pins. There is a lot of filler between the deck and interior shell so suspect the thickness varies.

Where's Larry Brandt???

Hey! I was out rebedding my starboard upper chainplate, which I myself caused to leak by being overly enthusiastic with a pressure washer. It was a slam dunk easy job. Of course I used BUTYL TAPE ala' Maine Sail.

I discovered several interesting things during this job. 1) When I dug out the old sealant I discovered that Catalina had done a very nice job of tapering the top of the opening as is supposed to be done; 2) that there is no balsa or plywood core in that area at all...it is rock solid fiberglass about an inch think. Solid as a bomb shelter! I came away from the task even more impressed with the C-36, if that can be possible! and 3) My 2002 boat has never leaked at any other chainplate opening, or any other opening for that matter. All deck fittings after a dozen years appears to be dry as a bone up here in the Pacific Northwest where it rains, and rains, and...

So the answer is NO, NEVER USE 5200 to seal anything on a boat (with the single exception, documented elsewhere on this Forum, of the inspection port threads on the plastic water tanks. 5200 doesn't permanently stick to the plastic tank material and so will keep the inspection port caps from leaking when the tanks are overfilled. The caps sealed with 5200 can be easily opened when needed.)

[I took a bunch of photos so I need to write this up when my life gets to be more organized.]

For the record, I have switched to the butyl tape and thrown the 5200 away. Wish I had learned that earlier.  The tape is wonderful - why did anyone try to invent anything to replace it?

I would go back and delete the prior post but the system doesn't allow.  If any of the admin's want to do it for me feel free in case someone doesn't read all the way down.