How about making it a pop up camper? It would help reduce the weight of the trailer and you would have less wind resistance. Also are you planning on using aluminum or steel for the frame? I would recommend using steel for the frame. A one inch angle iron would provide enough support for you to sleep on. You can use a 1/2 square tubing as a cross bracing. Talk with your local welding shop, they will be able to provide you with more weights on the different metals that would be feasible to use.