I'm going to go out on a limb and mention Down To Earth trailers. I have looked long and hard at trailers and am in the process of taking on the Down To Earth line. I think that from a value per dollar spent point of view, they are hard to beat!
The 7,000 lb equipment trailer they make has 6" channel main frame and tongue, 3" channel cross members, stand up ramps with the built in stands so you don't pick the truck up, and they won't even build one without brakes on BOTH axles. There are plenty of stake pockets on them for tie down points too.
I would buy the 18" at least if you plan on hauling more than just the tractor and loader and 20" may be even better.
Another thing to look at would be to upgrade to a 10,000LB trailer. For the little more it will cost, you won't need to swest it if you use it to haul lumber or building materials and you may just get a bigger truck next time too.
Where I live, as long as you stay at 10,000lbs or less, there are no problems with registration but 10,001 and over, I need combination plates and a medical card!
Ken