It has been brought to my attention that I should post the specs of the container I recommend using with the trailer.
It is a Rubbermaid ActionPacker, model 1172, 24gal, 90.8L, 26.5x19.3x17.4in, or 67.3x49x44.2cm
I get them at my local Lowes Hardware store for about $30 new.
Other containers may work too, that is just the one I recommend.
I am excited to see what others come up with for tubs or flat decks.