We had southern cross canvas custom make us bag that fits between the floor supports when the camper is packed up. It can fit a couple of coleman instant 4p tents my daughters Oztent stretcher and at least a few chairs + more. It has heavy duty straps on it that use the supports to clip on so no need for extra tieing down. The great thing about it doubles as waterproof storage when we are on site which we stick under the trailer and extra gear like chair and stretcher covers can be thrown in and is protected from rain, animals etc.
