Finally.
I got a call from ADOT. I was told directly from the Director Office of the the fuel tax that, the Director himself had reviewed my question and tho it is not specifically written private RVs over 26k are exempt from the 26¢ use fuel tax and are to pay the 18¢ light vehicle fuel tax.
I was given many reasons basically because we have a declared weight of zero, they are private, and they are used for living in same as a home.
So we have our official answer. Unfortunately they can send nothing to reference because it is specifically not written but compiled from various sections of the statues. Mainly zero declared gross weight.