I do not believe that the motor changes direction on this model. (but I could be wrong). Should you someday wish to do 4x5 sheets then the Unicolor is the only good drum for this due to the internal ribbing.
IMHO I would only wish to buy a drum set once, which I did, and would only buy the Unicolor drum and motorized roller.
Sean, I have been using a Unicolor Drum with a Simma motor base for a while now and have had no problems with developing 4x5 negs. My motor base does not change direction but the rollers are not quite round and causes a wave action inside the drum as the ends move up and down opposite to each other as it rolls. I've only used it for film but it seems to work fine.