Looks good, Ray!
One thing you may want to think about-
With your woodworking skills, you could easily build the enclosure out of something like 1/2" baltic birch ply, then have it sprayed with line-x or similiar to weatherproof/toughen it! Cost vs. sheet steel should be fairly close, but you'd have better ability to trim it out the way you want. If you go that route plan on at least 1/8" clearance at moving parts, lids, etc.
Why 1/8"? Frame twist issues?
I'll likely put a water tight rubber bead around the whole top mating surfaces so it stays dry even under torrential rains or during fordyce crossings! <img src="/forums/images/graemlins/lol.gif" alt="" />
Regarding the use of wood, yes, I was thinking of using wood for easy of fabrication and simply making a simple box using 2x12's for toughness and 1/2"-3/4" ply for the floor & lids. That would keep it simple and also make it easy to repair if necessary. Painting it with rhino liner/line-x is a good idea.
Based on my drawings I'll need ~30' (26.5' actually) of 2x4x.120" tubing and a few other pieces of steel (hitch receiver, etc.
Also, I spoke with one of the regional licensed makers of UCF torsion axles (T: 714 744 8425) and he said there are effectively only a handful of companies making torsion axles. Of those he considers UCF to be the best for wheeling for several reasons but most specifically it has removeable spindles so if you break one it can easily be replaced. Dexter & Alcor Corben are the other two major brands and their spindles are not replaceable.
He also said I was better off using a full width axle rather than a half axle because of the ease of installation and also better clearance (half axles usually require full width support tube anyway for proper alignment and with a narrow trailer like mine, I would only gain a few inches of tube free design at the cost of a more complex installation.
When you order them they're built to width as needed and it will cost me $259 for a 3200lb unit (minimum size w/ 6x5.5" lug pattern hubs). Also, I can request whatever angle I want (up to 45*) in the spindle to get the maximum clearance possible. <img src="/forums/images/graemlins/kewl.gif" alt="" />
Weight isn't light (~150lbs) but is probably the same as a leaf sprung set up.
Also said that off road, the trailer leaf's (unless very heavy) won't handle the weight and will fatigue and fail earlier than normal.
Also, any input regarding the width of the tires? The design above is the equal of the track of my Montero but I'm not sure if it should be less than the track of the Monty or the same. Perhaps it doesn't matter so long as the trailer doesn't tip over easily. What do you guys think?