As you can see by Arlene's post this was handed down from the Naches Ranger Dist. The PNW had nothing to do with the determination. This size limit came to the PNW in the form of an e-mail.
NRTP selection Committee member
Cle Elum Ranger Dist. ORV Ranger
Build your rig to fit the trails, don't change the trails to fit your rig!