I have the "standard" modification to my
Bigfoot, which is the straight
axle. It came with the 4" drop
axle and I switched to a straight
axle. Any more lift than that would be too much.
I take my camper down roads in southern Utah, which beat any typical dirt road in Montana, and I've decided that any road which would require more clearance is a road I shouldn't be taking my trailer down.
But on those roads, I'm going SLOW. So yeah, some scraping of the bumper and black/grey water drain valves. Not a big deal in sand. Slickrock...would be a different deal. I guess you just need to expect some damage. I'm not building skid plates for my trailer.
Washboard kills everything. Vehicle included. If you want to
rally down washboard roads, you just need to expect to break things. I have friends who have towed a Nash trailer all over the US, and live at the southern tip of Baja in the winter. They haul (by which I mean drive fast
) down rough roads. And have had their frame welded multiple times...But as far as I know their camper has help up otherwise. I personally think molded fiberglass campers would hold up a bit better than the average stick built.
But nothing is built to stand up to washboard. It just rattles everything apart.
I also traveled all over the intermountain west and southwest in a 2wd 1978 Toyota Chinook. Traveling in a motorhome lets you know what dirt roads are like inside the trailer. Driving dirt roads in that camper, with the "camper" area just a foot behind my head, made me realize what washboard and rough roads are doing to your camper as you drive down them. My drive into Chaco Canyon, on it's washboard, was a
long, slow drive. I couldn't go more than 15 mph without feeling like the camper was going to disintegrate...And driving down roads with huge dips or up over slick rock outcroppings and hearing the fiberglass crack and creak...I carry that feeling with me when I'm puling my trailer down rough roads.
Anyway. Huge difference between "4x4" roads and "dirt" roads, or washboard roads. Dirt and washboard don't necessarily require 4wd
or clearance. But they may well rattle you apart.
Actual 4x4 roads which require clearance and/or 4wd are a totally different deal. I don't enjoy bringing my camper very far down those roads (or rough, washboard roads for that matter. I drive them every day and the thought of bringing my trailer down any of them brings a lot of anxiety into my life...). At that point, for me, it's time to either leave the camper at home, or park it somewhere and car camp along the 4x4 road, then pick the trailer back up later.
If you want a camper that works for those kinds of roads...find a used (rare) 4x4 Toyota Sunrader, or find an old Chinook motorhome and transplant it onto a 4x4 truck body.
In my opinion rallying down dirt roads with
any kind of trailer = "no thanks". Not safe, not smart, not fun.
In the end do what you want, obviously. Buy something knowing you're using it in a way it wasn't intended, and beat it to death. I live and work in an area that is rough on things. If you want to use things in a certain way, you just expect to be replacing them fairly often. Your budget and attachment to things will determine what type of stuff you're willing to destroy.
In the end, any kind of camper will suit your needs. Depending on the type you get, it might need a little lift or something. But it'll all start showing it's use/age real fast.
If you're just talking about somewhat gently hauling a trailer down typical Forest Service roads, you can ignore most of that. Any old trailer will do, maybe with a little lift. The shorter the better.