Sorry, I got carried away there. You don't need a drum that does 20x24" prints to develop a 4x5" sheet of film. That might be considered overkill. The link below explains the basics for doing film/print in the unicolor make drum. Personally I use the Chromega Daylight Processing drum with Uniroller Model 352. The drum has adjustable rods to accomodate 9x12, 4x5, 5x7, 8x10 film or paper. It also has less tendency to leak.

http://www.largeformatphotography.info/unicolor/

Cheers!