Hi Martin , just to add possibly another braking solution to your rs. I believe the front disc from a cb 750/900 of the same period (early 80,s ) bolts straight onto the rs hub, then you can an use an XBR calliper however I think approx 2mm needs to be machined of the calliper carrier for it to line up correctly with the "new" disc. Maybe the super dream disc as suggested by dicksracther is the same as the 750/900, not sure. Keep us posted of developments, best regards Michael