A friend of mine built out a fatbike for an expedition into Salsipuedes Canyon north of Bahia De Los Angeles, Baja a few years ago. You can check out the planing and report here: Salsipuedes Canyon by Fatbike
. Planning first ten pages, report and pics start on page 11.
I met up with him at the end of the trip to give him a ride back north and was so impressed with how the bike handled the sand-dunes I bought the bike and third wheel off of him when we got back. I use it for beachcombing and backup transport in case I have to make a trip out if something goes south when we're off the beaten path.
I'm thinking of adding pedal-assist to extend range and improve fun, recharge batteries off of the solar.
Some pics from my buddies thread from the trip:
First pic: Thin Canadian and rig. The third-wheel helped him bring along gear and enough water to make it into the canyon and down to the Sea of Cortez. He brought along a setup to distill seawater when he got there.
Second Pic: Rig set up to go
Third Pic: Packraft set up to head down the coast. My buddy is from British Columbia. Apparently, they make an inflatable packraft that you can cut up a moose and raft it back to camp with when you're out in the boonies hunting moose. It worked pretty well to load up his bike and gear when he got to the water and get him back to his starting point.