I did some searching and couldn't find anything on this topic.
Rickmans seemed to be much more commonly raced in the 60s/early 70s than Cheneys, yet Cheneys appear to be more popular for modern VMX. Why is that? Does a Cheney handle significantly better than a Rickman?
I address the question to bikes of the period. It sounds like it is possible to get a Cheney that has been modernized somewhat, and it may be that subtle improvements would convey an advantage.
cheers,
Michael