Well, here's my 'simple' method.
It was easier for me to wrap my head around the problem: For example, I just think of the Chump green meter to represent 140%. (30 foot scale is really 42.)
I use Post-Its. My meter on screen is 96 mm long. Divide that by 14. = 6.86 mm. That distance on my meter represents 10% of the scale's power. I carefully mark the Post-It.
For Tourney, meter represents 135% 96 divided by 13.5 = 7.1 mm. That's now 10%.
Etc with the other green speeds.
I put other general notes on the Post-Its, like % effect of rough, although this isn't as accurate with the newish flyer lies.