Thats what iwas on about when i posted above , i guess the rc30 is a 6" rim?

I have an nc30 but i do have a nc35 linkage which im preparing to put in. And i know aboht the nc35 wheel swap and the rs250, nsr and the vfr750. But im wondering about the ducati wheels what sort of adjustments/modifications are needed? Anything major because i might aswell bite the bullet and get the next nc35 rear that comes up.

Depends on what you call major?

Chances of another manufactureres wheel just bolting on are next to nothing.

Providing the inner hole is close then you wont need to drill / file / adjust too much, but then you need to make sure the offset is right or the wheel wont be in the correct place.

Probably just better to get an NC35 wheel

the RC30 uses a 5.5 inch rim, but its 18" too so you have even less chances of getting tyres to suit than the NC30's wheel - and that's of course overlooking the fit is quite different.
the VFR750 wheel conversion is cheaper and easier, but again if you must have the 17" just buy a RVF wheel, it fits and looks like original - job done