This thread is 4 years old. I hope the OP is already out sailing.
Personally, I'd just cut off an inch and install the $29 kit from Catalina Direct, with everything needed, including longer lag bolts and sealant. That's much quicker and simpler than fabricating a sleeve and pop riveting, for most folks.
Catalina Direct, publishers of the Catalina 22 and Catalina 25 Owner's Handbooks and the largest supplier of parts and Lewmar winches for Catalina Yachts in the country
www.catalinadirect.com
And I'd upgrade the mast raising system so that the mast can't sway or rotate, even in a side wind. If you already have the gin pole and mast-raising stays and tackle, you need to add two side stays to the end of the gin pole to prevent any rotation if the mast sways slightly sideways. Anchor the bottom of the pole stays to the same point as the mast-raising stays.
It's the combination of the mast's lateral sway and the mast's axial rotation that breaks mast tabernacles and gin poles. The system is no longer loaded solely in compression; and the misalignment creates a buckling force.