I'm talking about the feasibility of using 275mm 6 bolt rotors with a 6 bolt 750K wheel (in my case a Morris wheel), with the F2/3 forks and the later twin piston calipers, instead of the Comstar or 5 bolt spoke wheel. Why wouldn't the combination be compatible? If the 550 rotors are too thick, they can be thinned. The K hub mounts the right side rotor inboard by about 3mm, which can be corrected with spacers. What is the outside measurement across the F2/3 rotors?
The 6 bolt rotors are stainless steel, it's quite a bit of work to "thin" them, but you are right it's possible. However, thickness isn't really a problem unless there is dragging at rest (which I don't think there is). It does cut down on the braking feel range because the piston has to travel less to fully lock the wheel, but not something drastic.
If you have a morris 6 bolt wheel, why not try and find a 5 bolt wheel instead? They made them and they are out there.
For the amount of work you are doing to keep a spoked wheel, can I make a different suggestion? What about changing the front end entirely? GL1000 swap is popular and common.
you could get an early kz550 spoke wheel front end and do an ex500/ zx6 caliper conversion. Still a spoke wheel, 5.5mm discs, 36mm forks instead of 35mm, as much aftermarket support.
If you have single disc right now, you could just do the single disc DOHC spoke wheel upgrade. It's one of the dual piston calipers and rotors on a spoke wheel - will still look close to stock and be better than the single puck brake, it just won't be as good as dual discs.
