I was aksed my a member about using a 55 gallon and to post some pics. Don't think it's necessary for pics so I'll explain.
His concern is that he cut a hole in the side of the drum for the auger and approximately 50-100 ponds of coal cant be used by the worm.
Instead of the side cut a hole in the bottom of the drum, leaving about 4 inches around the edges. Place the drum on blocks over the auger. This will allow you utilize nearly the entire drum plus a little bit more. You of course could place it on two blocks, build a little containing wall.