I would keep it simple and light and do not put to much overkill in it. I have one that is manufactured in Hayfiedl , Iowa that is 16 feet by 6 feet and they use leaf springs. It is very simple. One end of the leaf spring is hooked to a two pieces of metal that a pin slides through to hook it. You take the pin out and a manual boat winch is hooked to the one end that unhooks by a pulley that is at the bottom where the cable goes down and than back up and lets the end go up or pull it down. You let it down with the winch after you pull the pin out and on the other end the leaf spring is hooked to pipe that goes across to the other side inside a tube. The wheels axles are rated for 3500 pounds and are attached to the leaf springs. When you move you crank the the one end of the leaf spring that is up in the air and down and insert the pin to make it secure. The winches are mounted up about two feet and a cable goes down and around a pulley and to the leaf spring.