I'm thinking 600lb bike but then the added weight of the trailer needs to factored in as well. I know some of the Aluma bike trailers are around 400lbs give or take. So, ballpark, you're looking at towing an estimated 1000lbs - once again give or take a little.
About the only refreshing thing about that is the lack of wind resistance...or at least not much wind resistance. Something to think about. If the trailer had a brakes...I would almost feel more comfortable towing the Smart with the Bike.
