How much weight can I put on a car rotisserie?

I just got done building that redwingsteel.com rotisserie. First victim will be my buddy's mustang, so if anything goes wrong, nothing important gets damaged. ;-)

That's one beefy unit if you follow the plans. I can see it holding the complete car, but I'm also guessing it's going to be a PITA to get balanced. Glad to see so many others have used that design. Makes me feel more confident in it.