Two Space Heaters on 30A FW

I had a 30A serviced 5th wheel and I used a portable AC in the summer and an additional heater in the winter. Bought a 50A adaptor that had two 30A connections. I cut off one of the 30A female receptacles and installed a female 15A receptacle in it's place. I then installed an outlet in the rig and fed it with a connection on the outside that I could plug a heavy duty extension cord into. The other end of the extension cord plugged into the installed 15A connection on the modified adaptor. This way I could have a higher powered outlet that is entirely independent from the rig's 30A service. One main reason I did this is because we would sometime leave the pets in the rig during the summer and if the 30A pedestal breaker faulted (which did happen frequently at some parks) we would have backup cooling in the rig. The added benefit was having the ability to use 2 space heaters without overloading the 30A service.