The front brake rotors are the same for XB, 1125 and 1190's. 5mm or 6mm won't matter. Just get your preference.
The stock rear sprocket is hub centric at 117mm but certainly not an 'interference fit'. The slightly bigger hub diameter on the steel JT sprocket shouldn't make any difference. IMO, I'd put a small (1-1.5mm) o-ring on the hub to center it and torque to spec. If one comes out with a 117mm hub I'd buy it, but for now the 120mm works just fine on my SX.