This "A frame" design is patterned off others on this site. A Dexter torflex #8 axle provides significant structural strength. The Rectangular portion composed of 1" angle is probably structurally superfluous. It does provide convenient anchoring spots for the rear lights and leveling jacks. Andrew's chart indicated that 11 gauge, 2"x1" rectangular tubing is sufficiently strong enough for a foamy cabin weighing under 700 lb. The floor was was a plywood foam composite and added significant stiffness and strength.
