I've not tinkered with that packet yet, but I've wondered: Does it apply the weight/restriction to the car directly or just tell you to change it if it's not right? If I pit and rejoin, does the change stick or does the packet need sending again?
I have a multi-class thing in planning, but I wasn't going to use IS_HCP for it... I'll want two classes of the same base car for some races and I'm not going to have two ways of doing it going on at the same time. I'll just tell players what to do, and then check on IS_NPL and spec the non-compliant.