I sucked at high school algebra, but I'm thinking we need more than high school level algebra to measure the lean angle where pedal strike occurs on a bike with a rider.

Without your weight on the bike this measurement is meaningless. If we accept the fact that 2.5mm makes a noticeable difference in pedal strike, then the tire compression from a 150 pound rider is going to change both effective top tube height, and the angle at which pedal strike occurs. Then we need to recognize that centrifugal force add additional pressure further compressing the tires while turning. Is the additional compression significant? I don't know, but to measure the additional force applied we need to know what speed the rider will be traveling at the point where pedal strike occurs so that we (and by we I mean someone who can do math not me) can calculate the quantity of any additional compression in the tires. I also wonder wether side-wall deformation of the tire while leaned might make a difference.

Basically what I'm trying to say is that although I don't know a lot of math I understand the variables involved in calculating this, and I think you are leaving out a lot of important ones. WIth your method we learn the lean angle of a static riderless bike, but what we really want to know is how far we can lean over while riding.

Besides if that's all you want to know why not just get someone to hold the bike with the tires up against the wall, and put a protractor up against the center line of the back tire?