Hi Mark
If it helps, I fitted the S46HR1C1S to my S2R 1000. It was the DU333, which is actually listed as being for the S4R. The only shock that Öhlins specify for the S2R is the DU321, which is a much lower spec. version (S46DR1).
Both shocks have a length of 305mm. The DU333 has a stroke of 65mm. Assuming RCF's shock is the DU333, then it's actually designed for your bike so you'll be in luck!