I got the cleats off, but still don't have an answer. I swear that who ever built this boat had one guy working port side, and another working starboard. Port side seems well done, starboard must have been the apprentice who didn't give a rip.
The port side cleat screws were tough but turned out no problem. The cleat came off the rail sweetly. Starboard side ... as soon as I loosened the screws the nuts below must have been turning. I resorted to using a 5" angle grinder. Yep, gouged the teak. (dagnabit!)
The boom gallows had 9 lag bolts each side. through the teak & cap rail. Heavily caulked - no leaks. I guess the rationale here is that there isn't much upward / lateral weight to take so the lag bolts are sufficient.