What I generally do is use the rim, i use the wheel base gauge because the tab sticks out and gives you an attachment point. If you measure, then roll the car so the wheel turns 180 degrees and measure again it will help with identifying a bent wheel or axle. i set up alot of cars so i use Lasers, the method you are talking about is just as good. I keep a set of wheels with tires that i know are straight, this eliminates the wheel issue, but i still roll the 180 to check the axles, this is so that I can make sure my squaring numbers are good. This method is really simple and ANYONE can do it, its very accurate and takes little investment if any to do it. You can always call me and I will be happy to help.
Dennis Knox
Buckeye Legends
330-310-9212