[Graham]

5) Chassis choice would be different for each event, the "Super Touring Cars" probably restricted to all 3d chassis, the over 2.0 litre cars could be more open to B&W or metal.

Best to change the word "metal" to steel.

Either that, or someone might show up with an aluminum chassis.

Technically speaking Aluminium chassis are permitted (under the Metal) criteria. I have no issue with them.
interesting if you compare the 2 B&W chassis cars in the current proxy you might be thinking they would have a similar advantage, but the construction of them is totally different and although they have different powered motors I would suggest the main difference in performance is mostly because of the way the 2 B&W chassis vary in construction.

One issue I do have is that these "Metal or B&W" scratchbuild chassis are obviously not commercially available to all the entrants, and do offer an advantage over the plastic based chassis in terms of basic stability. So I do now attempt to restrict them to an Event where perhaps they are less likely to be advantageous to the other plastic based chassis cars.

As a matter of interest I measured a Revoslot BMW 2002 & Ford Escort today which has a rear wheel/tyre width of 50mm, so should I include metal chassis in the early era Under 2.0L event ??? Perhaps inevitably we will be looking at using 2 Classes in this event for plastic and metal chassis cars ?