I think the VYC yarstick system is a bloody joke and a shambolic mess. Darryl's post confirms that belief.
As a previous post mentioned, only 5 cat classes have ratings which are considered by VYC as "reliable", whatever that means. This is a clear admission by VYC that they have no confidence in their own ratings.
A performance based yardstick system would require a sophisticated analysis of data collected annually from several hundred races covering all classes and all conditions to be statistically significant. I seriously doubt if VYC has the resources to undertake such a task.
I'd suggest that the Texel system is a fairer and more robust alternatve for mixed cat racing in Oz. Give VYC the boot!
Phile