Briefly: you need to get both sources to the same frame rate. And you should NOT do this in FCP.
So: as converting UP is WAY better than the other direction: frame rate convert the 24fps 5d stuff, to 30 (ie. 23.98 to 29.97). You can then drop both into a 30fps timeline and you can add a DEINTERLACE filter to the 60i HDV stuff. I cut many commercials shot and edited at 24 and then convert them to 30 using Compressor’s best Optical Flow technology, so I know it’s good.
Ken Stones excellent article explains how to use Compressor to do very good frame rate conversions. https://www.kenstone.net/fcp_homepage/converting_frame_rates_compressor.html
It’s very time consuming though. Maybe you could do pre-assemblies or rough cuts of the 5d stuff – editing in a 24fps timeline – then frame convert that, instead of all the original; rushes.
Obviously a Pro-Res timeline is best so, if you haven’t already done it – you must also transcode the 5d’s H.264 sources into Pro-Res. Then do the frame rate conversion.*
* mmm …. you could try using MPEG Streamclip to both transcode the 5d source into ProRes AND a rough and ready frame rate conversion (24 to 30) AT THE SAME TIME. If you are pushed for time .. but as Daniel Low says elsewhere in this forum: ” MPEG Streamclip is not a great transcoder, although it is a great tool.. Frames/Fields will be doubled and fudged rather than have any complex ‘interpolation’ or calculations applied”
Hope that helps.
Jon Felix
DIGIT POST
Marin County, California