NEVER use metal for a chassis if it will be electric. Major glitches!
I know some one who was going to try to make his own chassis and would have spent 3 times more than if he would have just bought one and had a lot more headaches. There are so many companies making cars, it's not worth it to make a home made car. I know there are people who like to do stuff like that, but my 2 cents worth.