Trying to make black and white prints directly from color negatives isn't as simple as it sounds. A few pan sensitive papers have been made in limited sizes, but are not always available. But here's one of the problems : color negatives tend to be very low contrast compared to black and white negs. They have standardized processing and end up with an orange mask, both of which limit their contrast. So you might end up with a blaah result.
I've had to resort to a double negative technique to get serious punch. First, make a black and white pan film inter-positive from your color neg original, modifying it as desired using colored contrast filters (a bit of an involved topic, because you have to factor in both that orange mask, as well as the fact you are working in double negative mode - for example, if you wish to darken a blue sky, you add blue filtration to the enlarger rather than yellow or red). The nice thing, is that once you have processed your interpositive, you can actually see how the tonality of the final print will come out, because it is positive. Develop it to medium contrast.
Second, generate the actual printing negative from the inter-positive. This should be developed to a somewhat higher contrast. Ideally print it on VC paper, which gives you even more contrast control.
Per drum development. Jobo rigs run at a higher RPM than ideal. This means that development will be accelerated, and if so, the fill and drain times will become a larger factor in the shorter timing cycle, given the fact that Jobo drums fill and drain comparatively slowly due to their small opening. Due to that, I'd opt for a low RPM setting, along with manual fill and drain.
Another issue : Certain current papers like Ilford Classic and Cooltone are rather sensitive, and might show uneven highlights if the transition between solutions is not fast enough. The pump system of the ATL isn't friendly in that regard. So you will need to experiment.
But what Ilford paper is still available in any kind of graded fashion? Are you buying old paper? If it's a "digital" laser exposure paper as Koraks identifies it, will conventional optical enlargement even give you a truly neutral gray scale? I guess you'll have to find out for yourself.
It would seem so much easier just to work with trays and conventional VC papers.
