@McLaren @AMR Matthijs @RolexGTP
There's a workaround for the multiclass grids.
Make your race with all the settings you want except the track, just put the track on someplace random. Confirm the settings so it loads into the race and shows your car in pitlane and populates the AI. Then go Event > Driver List and press A on an AI car and choose "Change Car Group" and put it in the group you want it. It will change their group but it will glitch and won't change their car, but that's fine. After you have all your groups spread out evenly, change the track to the track you actually want to race at, and when the game loads into the new track it will re-populate the AI cars and put them in a correct car for the class they are in.
Note that if you go through and change any of the restrictions with the buckets (like if you realize it was adding in a TA car but you only want GT3/GTE or whatever), you will have to manually go change car groups again, and reload into another track again.
I had figured this out like 2 weeks after the game came out when I was actually doing a few Free Play races but forgot how to do it as I have just been doing organized league stuff since. I've been fiddling around with it for like 20 minutes trying to remember how I did it, I wondered if it had been patched but finally found the combination.