My wife doesn't understand my fascination with trailers, I guess, but I decided we needed another one.
I was thinking we needed something light, as fuel economy on a cross country trip is bad enough. The roof tent will stay on the roof, so the trailer will provide weatherproof storage for canopies, chairs, clothes, tools etc while the small trunk of the Discovery will be filled with a fridge and kid stuff.
Thule trailers, made by Brenderup, seem to make a good start for those without the time to build something from scratch. The one I just got is a 3205, which is 5x7 with a water-tight (allegedly) ABS streamlined cap. Empty weight 330lbs, 1330lbs payload capacity.
The plan is to put a flat deck across the front half, so small items such as sleeping bags etc can be on top of the trailer, but under the streamlined plastic roof when closed. Under the deck in front will be a water tank, propane water heater (modified Zodi), a couple of Orbital XCD batteries. The rear half of the trailer will be for other assorted "whatever" stuff.
The small tires are an immediate concern and I'll look into making spacers to raise the trailer on the axle and fit larger wheels/tires... but I don't get the trailer until the July 4th weekend. I got the last one left that I know of in the US and it's being dropped off in Ohio at a relative's house for me to pick up in July.
There's an accessory side panel extension kit to raise the sides from 14" to 28" but I can't find them anywhere in the US, so I'll have to wait for those later.

Any suggestions, or am I polishing a turd or ???

Is the axle is offset toward the rear of the box some, or centered on the box?

If it's centered, make sure you put the heavy stuff in the front of the trailer, or you're going to have swaying problems from not enough tongue weight. Putting the batteries and water tank in the very front is a good start. Maybe even build a box to mount the batteries outside the box, to get them more forward? Put the spare tire on the tongue too.

I've got a little 4x6 angle iron trailer that I bought for little stuff, and can be pulled by our Jetta or Minivan when we're not driving a truck. It came with the axle centered on the "deck". I added a spare tire to the tongue, but even with that, it's very hard to get enough tongue weight if you're packing the trailer full. I mount a car-top carrier to it for road trips, and because the front of the carrier is sloped just like yours, it's easy to get a lot more stuff toward the rear than in the short front of it. It would be nice not to have to spend so much time working on the tongue weight each time I pack it. I'll probably eventually cut the axle mounts and move it back a little.

The nice thing about a trailer this light is that a bathroom scale has enough capacity to weigh your tongue weight! :) Or I just pick up on the tongue by hand to take the slack out of the coupler to feel the weight, since it's never more than 100 pounds, and usually more like 0-40.

Pic of mine hauling future rain barrels from a friend's house last weekend is below. Even with that 3rd barrel all the way up front on top, there was barely any tongue weight. If the trailer had a steel tailgate (like to drive a riding mower up on), it would have negative tongue weight.

http://www.triadfoundry.com/richards_pictures/barrel1_s.jpg

Good point on the balance thing. It appears the axle is slightly towards the rear, based on the pics. I was thinking about a box on frame in front, but now I'm thinking a battery box with a spare tire mount underneath. Once I find out more about how the axle is attached, maybe when lifting it for larger wheels/tires I can make the lift bracket move the axle slightly more to the rear.

If you leave the paved road with a Thule/Brenderup trailer it'll just fall apart:homer:
Guess how I know:mad3:
They're not even strong enough to hold their own weight off road.
Have you ever seen one in person yet ? Polishing a turd is a good term to describe it, though. You can use it to haul stuff from the hardware store to build a good trailer, but that's it.

The trailer isn't really intended to go down anything more than a fire road, I'm thinking. I had a trailer intended for trail use once before but it was built so heavy that it made running trails with it absolutely no fun. I'm thinking we'll set up a camp, leave the trailer behind to run trails etc without it. When we do cross country drives, we camp at places that aren't 'extreme' as far as access. The heaviest stuff it would see would probably be done slowly and the light weight would pay off huge.
I can always mod the trailer a little if it needs some reinforcement for general use.
I knew it wouldn't be terribly strong when I saw the empty weight at only 330lbs, but running some aluminum bar stock around the perimeter to stiffen it up wouldn't add a lot of weight.
Then again, this might end up being a cluster F and I'll build something different.