I have a spectacular porsche paint job in the works for the upcoming Grand-Am series. I wanted to drive the classic track NAGT race at Osterreichring with it, but when I try to join the server with that car, I get booted for bad car.

The skin (or car?) is in the following folder:

rFactor/GameData/Vehicles/NAGT_VEH/NAGT/996/996_Generic

And is three files:

Infernal1.dds
Infernal1.veh
Infernal1WINDOW.dds

When I choose this one from the car listings in the vehicle menu, it's actually a separate team. Is this a matter of the server needing to have this installed for it to work? Or is it filtered? Has anyone had troubles running custom skins on NAGT servers?

.veh file is your problem.

If you create .veh, you're creating a new seperate car which the server doesn't have.

Do this:
Under 996_generic, create a folder called SKINS
Put in that skins folder: infernal1.dds, infernal1window.dds, and also infernal1.txt

The .txt file is just plain text, you can put your name in there as the painter. (The contents of inferna1.txt is what shows up in the car selection menu description box in game)

Like this:
Description="SoCal Motorsports #8 Jerry Chen"

Painter="Conor McCarrell"

Now in game, go to the skins tab and you'll see your skin.

Thanks much Jerry. That did the trick.