I got a digital unit and made a frame from a level that fits on the rim. It is availble for loan. While using it I found the at my wheel type protractor was off enought to matter.

Roll it back and forth and bounce it some. If the car has been up for a while(days) let it sit for a couple hours before setting hights. Legal street driving has a hard time getting tires up to usefull temps but you can get tunning temps when you push it some. I have a road near my house that I use for "testing" Someday I expect a homeowner to call the cops on "That damm loud green car" that rips by now and again.