I've started to use x-ray duplicating film and haven't had any contrast issues. It faithfully duplicates the contrast of the original negative, so that may be your issue. Are you trying to increase the contrast of the original neg? I'm not overly impressed with most of the alt process work I see from digital negs--lots of overdone photoshop, loss of definition, artifacts. Not to say you can't make high quality digital negs, but they're no panacea in terms of effort, skill, and cost.