I think Class 1 should be for standard K and Sigma cars - no tweeks other than the slightly raised rev limit for the Sigma's. Class 2 should be for standard Supersport K's. No porting of heads on any capacity. No Z and F stuff as produced from the factory and would include Sigma cars also all on 1a tyres. Class 3 would encompass all the evolved k's etc up to 160bhp anything goes on 1b tyres. Class 4 - leave it alone. Class 5 - upto 230 bhp which catches most big K including R500 and all H pattern boxes. Class 6 absolutely anything goes. Supercharged, Bike and sequential boxes. but 1b tyres. Class 7 as it is.