one thing I would add, that I haven't really seen anybody really bring up, is to lean toward the heavy side on the trailer.
I know alot of people like to keep things as light as possible, makes less work for the tow rig and such.....but...
assuming you've got a little extra tow rig to spare....I can't imagine a situation where I'd rather have a 7000# trailer vs. a 12k# trailer...
bigger axles/bearings/brakes/frame....
granted, the one time I had my 'zuk on the trailer, it was kinda goofy, as the trailer weighs more than the 'zuk....
but, I just feel better w/ a little 'extra' trailer....
that, and, especially now'a'days....most everybody has a 3/4 ton + tow rig, and a heavier trailer will be 8 lug w/ 16's....and those tires are about the easiest to find in the world.
one year on the way back home from Moab, Hugh was using 'what I believe to be' 10k# trailer, but it had odd-ball 6-lug 15" wheels on it, and special D-rated trailer tires (the only 15" tires w/ any sort of actual load rating)
well, at 3:00AM sunday morning, that tire is virtually IMPOSSIBLE to find....
where-as, my 235/85-16's we std. eqpt on virtually every 3/4 and 1 ton truck ever sold, and if you absolutely needed one and couldn't find a 24 hour walmart or something, you could always steal the spare tire from a truck in a parking lot and leave a $100 bill under the wiper
and being able to share spare tires between trailer and tow rig (in a pinch) could be a huge bonus....
(I'm always paranoid about losing tires, and usually roll w/ lots of spares)
--B