I'm out in the barn working on my jeep. I just grabbed my michigan vehicle code that I keep in my glovebox.
Vehicle code 710c:
"bumpers are required on any passenger vehicle, including 4 wheel drive and pickups. No more then 22 inches from the ground"
"Suspension modification can not defeat safe operation of the vehicle"
I'm 29" up front, and 27" in the back. Never had a problem.
FYI, the commercial vehicle code stats that there are no rules governing bumpers.
And the reason why I carry this copy with me is because of vehicle code 708:
"All passenger vehicles must have an outside rear view mirror on the drivers side, properly adjusted. Outside rear view mirror on each window if view through rear window is obscured". May officers are surprised to know you don't need a rear view mirror or a passenger mirror.