Before I go do something crazy like pick up a trip that leaves Dec 31 and carries 5 days into January, can someone enlighten me as to how that may effect my January schedule?

I tried finding other threads on it and checking the scheduling hand book, but didn't find much. How does that credit effect the building of my January schedule? I'll also probably have CQ and am considering bidding reserve. Problem is I don't want to mess that stuff up by picking up a carry over trip if it will have a negative impact.