In the end, I only had to epoxy the Iwa so it would fit the 24.5" mast collar. I just filed the set screw hole a tiny bit to get it to fit otherwise.
For the Kai wing I also had to file the set screw hole, but the fit was closer so I only had to shim the collar with metal duct tape to get the fit tight. I still need to fine tune the M280 and the Nalu - but should be relatively easy.
Looking forward to playing with these again - especially the M200 and M280 on the 29.5" mast for windsurf wave foiling, and the Iwa on the 24.5" for surfing. I'd say the surgery was a success!