[Peter Giffen] “Is the 59.94 footage 24p shot over 59.94 (i.e. 24p shot over 720p60 with a 3:2 cadence) or true 59.94 (720p60)?
Honestly I am not sure “
Open one of the 59.94 clips in Quicktime player and step through the clip frame by frame. If the image changes every frame, it’s true 60p. If you see a repeating pattern of two duplicate images followed by three duplicate images, it’s 24p shot over 60p. If that’s the case and you want it to play nicely with the native 24p footage in the sequence, you’ll need to use FCP’s DVCPRO HD frame rate converter to remove the duplicate frames so that the 24p over 60p clips are conformed to true 24p.
Although you can mix formats and frame rats in an FCP timeline and have it play back, it’s only meant for preview purposes. FCP doesn’t do proper format conversion for rendered output. You’ll need to conform all of your clips to one format and frame rate prior to editing for proper output without artifacts.