And even the Super rocket was billed as the highly tuned motor. "with extra chrome"
i'm no RGS expert but the alloy rims and 190mm hub would have lost some weight from the bike and many RGS had a siamese pipe so one less muffler in weight.
They also may have had a race silencer
. But only marginally more power if any from a super rocket.
And as Muskrat alludes, the valve size limitations compared to the A65 meant what limited performance over a stock factory SR was most likely from Eddie Dows assembly not the pistons and cam.
Saw two genuine RGS's at the Nelson classic museum, nice but hard to justify the cost premium over a SR.
I guess if I came across one with some clear provenance I might be tempted
If you look at the spec for the American market Road Rockets in 54/55 (even twin carb options) they had all the best bits and were years before the RGS