I've shot a bunch of double system sound with the 5D and ZoomH4n, with the old Canon firmware, and preparing to shoot a short with the new (2.0.4) version. I've been using Pluraleyes with FCP, and changing the Zoom audio to 99% speed to maintain sync.

So with the new firmware, shooting at 24, anything I should be aware of regarding double system sync? Do I still need to reduce the speed of audio in FCP to 99%?

Audio drift should not be an issue with the new firmware since the framerates have been changed to 24 or 29.97 and the audio has been set to 48khz instead of 44.1khz.

Thanks for the reply--I didn't realize that the firmware updated the audio to 48. It's not true 24 though, it's 23.976, right?

You are correct. PAL 25p is an even 25, but 24p is 23.976.