Don’t know how you are getting on with this Keith, but I have found you can spring the yokes open a few thou with the help of a large screwdriver tip driven ( not too heavily ! ) into the tightening slot, as close as possible to the leg. This may cause a sucking-in of breath by some experts but it helped me.
I still needed to use worm clips though, fitted over tape protection, and holding a ratchet strap in place. Then it was easy.
I think it’s common to see a bit of the brass shim showing and I suppose with care it could be trimmed flush.
