I am using some rather thin wall 1.5X2 rectangle for most of the frame. I can't remember the thickness right now. There is a hunk of heavier 2x2.5 or 3 for the single member tongue, but that might get changed. I am thinking now of making a removable/adjustable tongue. Shorten it up for highway travel and then lengthen it for rough road where I might need the extra turning degrees. The axles are 1400 lb Flex Ride. I am not planning on brakes at this time but they could be installed. Then the adapters so I can use the wheels/spare tire of the tow vehicle. Now just watch me get a different one. The rims are from a 2000 Suzuki Vitara. It will be about 5 foot wide, about 9 foot long and about 4.5 feet high inside. Drop floor with left door to the bottom of it. Will be an adventure to make the frame strong enough going around a big hole in the rail. I am getting up in years and am not so flexible now days and making this for trips 1-2 months long. Don't know if I will use that ball hitch. It is a cheapy.
I started welding up the frame today. Still have a lot of pondering to do about it but the width is set. Wheels will be partially buried. I do not like wheels sticking way out wider than the TV and I need to cut down on air resistance.
It was 6 years ago today I started cutting metal for my first TD. Which was actually my 4th trailer. The others was farm trailers. The very fist one I built when I was a junior in high school. It was 8 wheels, tilt bed and could carry about 20,000 lbs. or more. That was in 1967-68. The 2nd was a sprinkler pipe trailer that I stumbled upon in Feb. I was surprised it had not been cut up for scrap. It was never very good.

Back bone of it was from a 1935 chev truck. If I remember correctly.

Used the front axle from same truck and flipped it over for ground clearance. I built this before I had very much experience with irrigation sprinkler pipe and it was never a good trailer. Like I said I was very surprised it had not been melted down.
Randy