We have a whole list of crap...
Tire tread must be covered
Bumper height maximum 27" to bottom of bumper on cars/SUV's (aka my BII)
There is a maximum headlamp/tail light height
Mudflaps must be used if the angle from tire contact surface to bumper is greater than a certain number
Windshield must have less than 10% surface area damaged (cracks, chips), any damage within driver's sightline auto fail
Basically, that's just the things they can see right at the side of the road. Pretty much, if you get pulled over and any of the above applies to your vehicle, you have to take it to a licensed inspection facility and have it inspected. Sucks.
Sorry for the threadjack. Continue with the awesome work!