Towed my 7x12 Enclosed with 6.5' interior height all summer. I converted it to a toy hauler. Weighs about 3100 with the bike and gear inside. I have trailer brakes. I highly recommend them if towing above 2500 with stock 4runner brakes.
I have Monroe shocks and OME 906 rear springs. They are perfect, nice and level when I put the trailer on.
I can maintain 65mph on the highway, even 70. Overdrive off obviously. I lose speed on big hills without flooring it. I get 10-12mpg. Transmission temps 140-170F with external transmission cooler.
Towed about 3000 miles this summer.