You could do what I do ... join a few C races, on the kind of courses that suit your strengths, and see how it goes. But stay in D for this series. I love having the choice of riding B when it suits and learning how to hang on to the B's whilst only pushing C numbers. At least then when you are thrown into C by ZP you'll know what to expect
If it helps, I think you rode really well last week in the CC race (ignoring your solo attack!) and held on to the group really well - we were pushing C numbers so I think you'll be surprised by how well you do on the right courses (stay away from the hills
)