the Alcan was still a lot of dirt when I built it - in fact it was seriously chatter-bumped in a lot of places. The Denali Highway is dirt too, and it was fine. Again - soft riding Subaru torsion bars are so easy on equipment - even hitting frost heaves that bumped my head on the ceiling of my tow rig the trailer did fine. It has more travel and softer suspension than the Ford.
That box went 15 thousand miles the first time I built it - lots of highway but lots of dirt too, I'd guess maybe 2000 miles between the Al-Can and other locations across the U.S. - I went thru like 37 states in 7 weeks. The only downside for the wood was letting it soak in the woods, some sections got saturated and began to rot - I just cut the worst out and applied paint a couple weeks ago.
It's not fully open inside too - there are vertical panels that divide it, so on one side a big door opens, and I stuck the jogger-stroller and camp chairs in that side, while on the other you can see I made a cook-area for the camp stove, and the stove resides in there with fuel and cooking utensils. Under that is a long narrow door I where stick fishing poles and such. Access from the back gets you in a 4-foot wide by 8 foot deep cavity - there is a front access door too, makes a good place to put campfire wood.
somewhere I have my own thread on this thing here....