The previous owner added a welded metal channel to an augmented bottom frame 48X96X 3.5" with foam insulation encapsulated between two sheets of .5" plywood. The 1x3" steel channel is cantilevered and supports a sturdy 3" thick wood platform 12" wide to support a 30 lb propane tank and the ladder. It is immensely strong and you can lift the back of the camper with my fork lift with no deflection.
