I don't see why more catsailors don't use tapered mainsheets. You can make your own, and mainsheets tapered to a smaller tail inside the blocks surely do run easier. Tapering makes Maffioli or its clones really nice.
I struggled for years with fat 1/2 inch mainsheets on Hobies until the revelation struck.

Dacarls:
A-class USA 196, USA 21, H18, H16
"Nothing that's any good works by itself. You got to make the damn thing work"- Thomas Edison