After the 29 consistant years that my family has been active in IT I think the following 5 things in order should be used to determine if 2 spec lines are needed.

#1 Does the car use the same Unibody. (So an MX5 and RX8 would NOT be the same since they use the same platform but have a different Unibody. Likwise a 4 door jetta vs. a 2 door jetta would be on seperate lines because they have a different unibody, or another example is a hatch vs a trunk would be seperated)

#2 Does it use the same engine type with same HP ratings, same disp, and same HP ratings. If components that are not allowed to be changed per the ITCs are different then research is required to make a transparent decision with facts on why we would or would not consider them on the same spec line. The only reason we would create a seperate spec line would be that we percieve a competition advantage could be had by creating a frankenstien car that was never produced.

#3 Driveline compatibility. Can everything be swapped around between models with no apparent competitive advantage greater than either classificiation on its own.

#4 Suspension design as used to determine the classification of the car. If 1 design is of greater design to warrent an "adder" in the classification of the car than it would need to be seperated onto a seperate line

#5 brakes as used to determine the classification of the car. If 1 design is of greater design to warrent an "adder" in the classification of the car than it would need to be seperated onto a seperate line


That is my simple thought process from the "racer" side of the fence
Stephen


PS: I did mention that we have raced activly in Improved Touring for 29years so that you would know and understand that IT is something that I have followed and participated in for a better part of my life. I have witnesed it transform through the good and the bad... and been part of it all.