Well .. the Vette's demoralized the GT-1 class so much that the Ferrari's and Aston Martin's refused to come play anymore.
It wasn't a 'race' at that point.
So they switched to GT-2, puttin smaller motors in their vettes ..and now it's 'a race' again without any sure bets.
At least until they get the new combination sorted out.
We all know why the Camaro isn't doin as well against the Mustang ..it's more than a bit heavier.
A lighter smaller car with equal horsepower will smoke the bigger heavier one every time.. drivers being relatively equal.
As for the IRS .. I know you know this but I will say it anyway.
It doesn't bump steer the back end over a rough spot like the 'girder' will and it keeps the tire aligned with the road vertically-horizontally under compression-extension if it's setup right. The trade off is more moving parts = more friction = more hp loss.
They don't use the 'girder' in F1 because that class winner is determined by how fast he can go on a road course with a limited amount of horsepower. Apparantly they can go faster with an IRS than with a girder despite the inherent horsepower loss.
I hate weight limited classes because the ruling body can 'adjust' the bias so literally anyone can win if they whine enough to the rule makers.
Classic example: the Hemi in Pro Stock NHRA ..ruled out of existence instead of competition stepping up their game.
Gimme a class where the fastest guy wins .. period.
Like Top Fuel (granted, .. they have a *minimum* weight ..you can build a heavier car if you want to

-Frank (just sayin)