People have swapped bearings to make the kxf hubs work. But, I think the spacer adapters from Warp 9 would be the easiest solution. They also said they use a custom cut rotor for the wheel like the one I have. It is $65 plus shipping. So if you are going through the effort of swapping wheels Warp 9 is not a bad way to go since you get a complete wheel all ready to go with rotor and sprocket for about $360 a wheel. But if you have a kxf wheel there are the bits to swap out too.
Good Luck
Alex