Like ic-racer, too much light has never been a problem with my color enlarger. The head has a built-in white attenuator, but I've never needed to use it.

OTH, cyan filtration along with yellow and magenta gives you ND anyway, though it would likely take some experimentation to figure out how adding some cyan affects the contrast. You would also need to use the "two-filter" Y/M filtering method. A meter would be helpful too, though not essential.