Please critique my home front-end alignment method

Yeah, I think I of figured out the advantages. It has two camber bubbles which should help increase accuracy. You turn the wheel 20 degrees one way then zero it out before turning it 20 the other so that would negate the calculations. I'm going to give my little harbor frieght angle finder and home made turn plates (plastic bags with wd40) a shot and see how close I can get before spending any money.