I would think an 8x10 drum would work for that. There are various threads around about using an 8x10 drum for processing 4x 4x5’s in a drum like this. It may take some experimentation to get it right.
Do these have the plastic "T" rail on the inside to catch the edges of the film? Or some other mechanism to prevent the film/paper from sticking base-side to the interior. Or is that how they're supposed to work?