Dan, At the end of the day, they can do what ever they like and if they
bend the rules, they change them in their favour.
I just got a speeding ticket from a truvelo forward facing camera.
I was in a long line of traffic doing about 30mph, I even saw the camera as I
approached and slowed down a bit.
Still got flashed and the speed was 34mph in a 30mph.
Having 18 inch wheels obviously makes your speedo under read.