Oh, trust me, I know ;) Kowa 16-H is the best bar-none. I've got a 37mm MIR-1b, a Konica 40mm as well as 24mm lenses in FD mount from Canon and Tamron . . . so I know how wide it can go. My plan is to eventually snag a 35mm f1.4 C/Y Zeiss, as well as a longer lens (probably the f2.0 135mm) . . . along with an appropriate speedbooster from Metabones. 5 lenses from 35-135mm strikes me as a pretty complete set, and with the speedboster, it's kinda like having 10 lenses.
I'm also in the final stages of development on a wireless follow-focus system that sync-focuses the prime and the Kowa, using Arduino-controlled stepper motors commanded by an Android app. But I'm keeping it mostly under wraps until such time as it's fully functional, at which time I'll do a nice write-up with instructions to make your own.