It will be interesting to see PeterW's reply.
Meanwhile, in the 1970s I ran a VH and Watsonian Monza sidecar which had highly polished steel flywheels which were completely flat on the outside and stamped C&H on the rims. I assume C&H stands for Carter and Hartley which was the dealership where Lawrence Hartley was a partner. Anyway, the big end began to knock so I acquired another set of flywheels, a new big end for them and swopped the flywheels over. The new flywheels were the heavier VG type. The improvement in performance was considerable. I have always thought that this might have been due to the extra weight of the sidecar. Perhaps the lighter flywheels are better for high revs racing but the heavier ones are better for low revs normal use.
36 4G, 37 VH, 53 ex ISDT KHA (project), 54 KH(A), Healey 1000/4 (project)
Former Machine Registrar & Archivist, General Secretary and Single Spares Organiser (over a 25 year period).
Now Archivist once more - but not Machine Registrar.