Well, mystery solved. The specs say the shrouds should be 7'8" above the mast datum (cuddy top). Mine were exactly one foot too low. Those old mounts were about 2" too low per the spec. So I'll move the new mounts up to the right location I guess. I'm really confused what that old mount is that's in almost the right place -- it has to be the spreader mount, but I don't find any mention of an alternate spreader style, and that mount lets the spreaders swing freely fore and aft -- I think compression on it would encourage the mast to twist.
GreenLake wrote:The shrouds on a DS (and the forestay) all attach partway up the mast. That location should be close to the location where the "jumper struts" (mini-spreaders) for the diamond stays were located.
The spreaders mount quite a few feet below that.
Actually my "diamond stay" is not the factory jumper stays at the top of the mast, raked back about 45 degrees and mounted above the forestay. (I removed those following some advise from this forum.) My boat's previous owner had installed a big diamond stay down lower, centered on the (apparently correct) spreader location and smack in the way of the jib leech when tacking, with struts made out of broad-headed, threaded, hardware-store carriage bolts that caught on everything.
The shrouds look correct; attached up by the forestay on reassuringly ancient hardware.
When I picked up the boat, the mastjack was painted over/sealed to the deck (prior owner never knew it could move), and the centerboard was installed upside-down so it would only deploy about 15 degrees. He said he only ever sailed it once; I guess it didn't perform too well for him.
Edit: Actually the spec mentions "7.10. The shrouds shall pass over spreaders, which may be of fixed, full swing, or limited swing type."
So I guess "full swing" spreaders are a thing. I am debating whether to drill new holes in the spreaders, so I can use them in the old apparently "full swing" lugs, or to drill new holes in the mast to re-mount the newer (apparently) "limited swing" brackets. The newer brackets definitely seem more secure and match the modern boats, but I hate the idea of drilling more holes in the mast. Gotta think on this one for a while.