Or you can use four straight, flat shims installed 90 degrees apart around the mast where it clamps in the rotator housing; each shim would need to be 1/4" thick, so 1/4" thick flat aluminum or steel stock can work.
This keeps the mast rotating concentrically. All the CDE ham radio rotators require shimming if a mast smaller diameter than 2-1/16" is used -- been that way for 5-6 decades.