I actually haven't heard of anyone doing it in this order though I am sure some do. i know several people including myself who took CP after residency and the AP after our Surgical Pathology fellowships. I have never been a great standardized test taker so this was a strategy for me to seperate them and concentrate on just one at a time. It worked for me, not to say I wouldn't have passed if I would have attempted both at the same time but for me it was worth the extra money to have a better shot of passing both. For me it worked and I passed both on the first time.
Positives: less to study for all at one time (less stress); possibly a better chance to pass
Negatives: it costs more to do them seperately..$1800 per exam ($3600 total) versus ~$2300 if you take them both at the same time, plus two trips and hotel stays in Tampa. Then again if you take them both at $2300 and fail one then you are looking at $2300 + $1800 = $4100 after you retake. i would recommend you look at the big picture including your strengths and weaknesses in training, you testing ability, available time to study, etc to make the decision that is best for your. As an aside, everyone I know who took them seperatedly ended up passing both. Good luck on your decision.
Pathguy11