Cycle-x dual Mikuni setup won't fit a stock frame, FWIW. You can physically get them in there, but the intake path is fooked. Can't run air filters, probably have to trim down the cheap stacks they come with. Not a good idea, and not recommended by Cycle-X. Again, just FWIW.
There's also the Mikuni RS setup that is about the same money as a set of CR's. But, they're pretty big (34mm!) and on a stock engine, that's probably a real torque killer.
29mm is probably too big too, I think you're probably dipping into mostly uncharted waters here. Maybe adapt some CR 26's?