Jabberwock said..
If you use them, screw them in, do not rivet them. This will allow you to remove them if you want to get at halyards at a later date. I have had to swap my halyards from port to starboard and they do restrict your ability to get into the mast.
The only other ones that may retro fit is the Harken big bullet 134
My old ones have a cut out of 96mm x 24mm
I'm gong to have a look at what brand yours are Jabberwock please
I intend to tap threads on a lot of fittings
I'm not to sure how nut certs would work on a mast I use them at work now and then that would be another way of fixing
you pull them down like a rivet
