I bought a steel 5x10 at Tractor Supply, figuring it would serve the purpose well. Soon after, I unexpectantly bought a 2nd four wheeler, to which, caused me to have one of those Homer Simpson "doh" moments.
So instead of trying to sell it and go through the headache of buying an even bigger one to haul 2 machines, I retrofitted the 5x10, by cutting away the front/side railings, on both sides in front of the wheel well/fender, essentially transforming the front half of the trailer into a flatbed (the rear side railings, behind the wheel well/fender, remained). This allows for easy side loading, using my old ramps, on either side. I ground down the sharp edges with an angle grinder, primed and repainted the newly cuy away area, added some tie-down "D" rings, and it looks and functions as though it were factory spec'd that way. The trailer has a larger GVWR, so hauling both of my quads on the trailer, "T" style, fits like a glove...albeit barely. (My 660 Grizzly on the front, sideways, and the wifes 300 Honda, straight, on the rear.)
The trailer has stake-pockets, so I built 2 wooden side rails to fit in the pockets, in the event that I haul something that requires closure on those now-open front/sides. And I can still haul my 12 ft row boat (upside down), building materials/lumber/plywood, firewood, lawn equipment or whatever.