I use the Unicolor kits too, and they are very consistant. I add 5 seconds to the developing time per roll of 36 exposure or 120 film. For the 24 exposure rolls I sort of guess a little less. I have no trouble getting twice the rolls the instructions suggest.
For consistant results you need to control temperature. I use a thermostatically controlled bath with a pump to move the water around the tank and bottles. Actually it is just a plastic dish pan, but temperature is very constant at 100 degrees F. I also had trouble with spotting. I add photo flo 1:500 and hang the film at a 45 degree angle with the edge down, no squeegee. No more spots!