It might be doable with a rig that size in Arizona, where there's tons of open ground. But since your target area is "the Northwest", I think the size/type of the contemplated rig will very severely limit your boondocking options.
I boondock almost exclusively and have done so all over Oregon/Washington. Many such locations are heavily timbered, and "roads" tend to be single-lane, poorly maintained if at all, and lack not just big turnarounds, but enough clearance height-and-width-wise for a vehicle that size.
My heavily Sierra-pinstriped but wonderfully nimble tug/tow combo is VERY small. Thirty feet stem-to-stern, 6'5" at its widest, 7'3" at its tallest, 4x4 traction, and articulated in the middle to boot.
Despite its size/maneuverability, there are many such places that even I can't go....and some I shouldn't have. As witness the busted trailer window I came home with recently, a result of a tree branch punching through it on one such road.