Hey, I went with the harborfrieght 40x48 and bought some angle iron... 13 inch wheels. Cost around $400 (including iron) ne. doubled the deck with 4 overlapping 3/4 inch plywood, then finished off with truck bed liner paint (spray). I also welded the angle iron and extended the tongue.
It works well, has been on the highway 3x 180 miles round trip.. I would say go at LEAST 13 inch wheels, and make sure you have some extra space to tie her down.
I was selling mine, but the title is screwed because of the modifications. Another $180 for inspection etc, so I ride with the old tag bent up so its out of sight. If I do sell it would be for next to nothing considering the title and inspection... $200 max (no resale)
If I were to do it all over again, I would go with a 5x10 or 4x8 with loading gate and the largest possible wheels (15) the trailer would fit. Something about flying down rt 80 at 75 mph.. to nervous although my current trailer has been good so far
My favorite are the ones lowes offers.. cost around 1200...