For those looking at getting a trailer, I'd HIGHLY recommend getting one with a tongue A-frame that is at least 4' long.
3' makes sharp cornering a problem, because the camper jacks may hit the trailer unless you have a long enough ball mount, or hitch extension.
In many cases, you will have to special order a trailer to get a 4' tongue.
The exception to that is Freeway Trailers in Fife, WA. They understand the need for a longer tongue and order all their trailers with at least a 4' tongue.
I'd also recommend 7' width, so you can see the darn thing while backing up. You can't see the trailer body, but you should be able to see the fenders.
My 6x12 was difficult to back up, because I couldn't see the trailer until it was crooked.