Gerry -
I have a unicolor drum and roller (left over from the old days when I did cibacrhome printing). So I was naturally interested in how well it would work for me in processing sheet film.
The 8x10 printing drum was thoughtfully designed to also accommodate 4x5 paper - there are y-shaped extrusions on the inside of the drum that creaates two 4" wide "grooves". You can process film in the drum by loading the sheets between these extrusions - emulsion-side in of course. To get the maximum four-sheet capacity from a drum, you need to put two sheets into each "groove", and something must be done to prevent them from sliding over each other. Unicolor supplied a small rubber wedge that would slip over the middle y-xhaped extrusion between sheets - if you are looking at used drums, the wedge will probably long since have been misplaced. But it shouldn't be hard to find a creative alternative - there's one web site that suggests using a small plastic clothes pin.
There were at least three printing drums on the market - Unicolor, Beseler, and Cibachrome. I think there may have also been a few aftermarket brands (Spiratone, for example). Unicolor and Beseler were the main brands for roller bases. Unicolor claimed that their roller base was better because it would periodically reverse the direction of rotation, while the Beseler base was unidirectional. I really don't know if there were any significant differences ibetween Unicolor and Beseler drums. I believe that both were single ended - you poured chemicals in and out the same end of the drum. Cibachrome drums were feed through - you poured in one end while draining out the other. I dont' think that difference would matter at all in processing film - it really would be a matter of what you become accustomed to using. Cibachrome did supply a 4x5 drum that would be useful to develop single sheets of film.
Drum processing involves a smaller quantity of chemical and continuous processing. Theh unicolor drum was designed to use 2 oz of chemical, and that should be fine for film. All things equal, continuous agitation will result in higher contrast than intermittent agitation, so to compensate you need to shorten the development time. I'm calibrated on HC-110 dilution H in trays with intermittent agitation, so my numbers won't work for you. You can probably find a starting point through some web research, but eventually you will need to arrive at your own calibration.
A lot of people use drums and are happy with the results they get. And it is definitely a practical option if you don't have a real darkroom. The one experience I had was not happy - the sheets slipped in the groove and ended up on top of each other causing the bottom sheet to not get full development. I used the rubber wedge, but it popped off the plastic extrusion part way through processing.
One final comment - changing bags are fine, but there's not a lot of room to work. That's a problem in loading holders, and I would think it's a bigger problem in loading a unicolor drum. I suggest that you look around the house to find a room that can be darkened completely while you change film. My wife and I spend time at a condo that is not equipped with a darkroom, and I have found that a windowless bathroom works perfectly - wait until after dark, make sure that there are no lights in the area outside the bathroom door, and stuff the bath mat under the door. Working on a sink gives you a lot more room to maneuver than working within the confines of a changing bag.
