I've got the GOG version and I'm having trouble getting forest to work. All the other cars and tracks (except slimepit) work, those two give me a "car behavior error" as soon as it would normally be going to the starting line of the race. I think FlyWheel had gotten a 3dfx version working back in the days.

I have the non-3dfx version (on the original CD I bought on the day pod retail was released in 1997) but I can't seem to get the non-3dfx version of pod running either. (It won't install because it thinks there's not enough space on C.) While the 3dfx version is prettier, the racing seems way slower because of the texture smoothing. Plus that original version didn't encrypt the car settings files and you could easily set your speed/accel etc to higher (even ridiculous) amounts. ;)

Anyway, has anyone been able to get forest or slimepit to work at all?

Set the difficulty to Hard.
Any other difficulty will raise the fatal Car behavior error on load.

Awesome, that did it. Thanks!

Good work on the file specs so far. Have you been able to write new values to the prb file yet? They encrypted that because I had shown them it was easy to just set your car's speed etc to way higher values... I recorded a ghost with a shivan going like 900 MPH down the straight in Beltane. (LOL, I still have that somewhere) But now that there's no ghost gallery or Game Service to worry about, it would be fun to tweak the car settings to make things faster but still driveable. :)

Yes, I played around with both formats (the public test tool doesn't support the unencrypted PRBs of the OEM version, but they can be easily modified with a hex-editor).

I might create an editor for the PRBs, but POD2 contains additional validations to clamp negative values and to verify the limits for specific game modes (I did not take the time to test if this is related to the online and/or ghost mode or if it depends on something else...).