...trying balance in say STU with all the cars that are eligible is going to mean competition adjustments such as brake kits and alternate engine allowances, at least that is how I perceive the classes future.

That's exactly the opposite of what should apply, if a weight/displacement formula is a first assumption. I don't LIKE the fact that it's going to leave some cars out in the cold but it's inconsistent to use a formula AND try to balance based on on-track performance with competition adjustments (bleah!). That's the worst of both worlds.

If there's any inclination to go that route, chuck the pretense of formulaic considerations and admit that success will result in weight penalties.

Instead, make the stoppers formulaic as well as the parts that make them go.

** Displacement = weight
** Max brake size
** Max number of gear ratios
** Max size of aero add-ons

Everything has to bolt to the stock shell.

Go.

K