Tom, it would hook right up to a mountain bike! All you do is take out the quick release from the back wheel and put it back on with this little hitch mount thing on it. It stays right on the bike, and you just connect the trailer hitch with a pin. It has a ball joint so the bike can lean against whatever, and the trailer stays flat on the ground. The whole thing folds up pretty small to go in the car. The floor is suspended over the axle, not right on it, to make it less bumpy. And a 24x36 dog bed fits in there perfectly.
It's very stable. Bella seemed to have a good time. Lots of sniffing and snorting going on back there. We passed one dog, and she didn't do anything. She liked the rest stop! She sat facing forward most of the time, and facing rearward a little bit of the time, and never laid down.