So far, you've done about what I would have. I'd only invest in a comparable condition set of original magna or perhaps target grips. I'm with the 'don't do a lot crowd, particularly refinishing. Unlikely an economic move. I believe the cylinder wear is commensurate with some of the big old honkin Highway Patrol style holsters, snug fit only accountable in the cylinder (widest point) area. Likely a lot of range time firing from holster. I have a 'pre' Model 21 4", exhibiting a bit of this type of predominant wear.

Congrats on a worthy Smith and enjoy!
My take