I, too, use an enclosed trailer. Mine is a 7x12 V-nose, all aluminum. Spyder drives up the ramp just fine, but it's an extra tall trailer, so the ramp is quite long. Nice thing is that I can chuck a couple of small bikes in there with the Spyder, plus gear. Without the Spyder it fits four bikes quite comfortably, plus we sleep in it after it's unloaded.
If you are going to be traveling around the country, look into the trailer laws. Some states require trailer brakes, even with as low as a 1,000 pound GVWR trailer. A small landscape trailer could require mods to be legal...or safe, especially in the mountains. Also, I'd avoid the narrower trailers. When the wheels are that close to the rails, something is gonna get dinged if you put it on and off enough, or it bounces around in transit. The Spyder wheel spokes stick out beyond the tires.
-Scotty