Found this other thread where they are discussing essentially the same issues.

http://www.dvinfo.net/conf/showthread.php?t=90038

Looks like the need to clip frames is evident (I must not have been paying attention). Anyway thanks for everyone's help here. At least I have something I can work with until either Canon (by flagging the stream) or Apple (by doing a magic cadence detection) make it easier on us. My guess is that iMovie will have HV20 1080p24 support before FCP does since there will be thousands of consumers soon who will be asking what is this 24p stuff all about and how do I do it!