YES - BUT
• External Hard Disk - MUST BE - Mac OS Extended (hfs) formatted (all mine are journaled)
• Should be FireWire or Thunderbolt - as USB/USB2 performs badly to me and especially when filling up.
• I do - create a folder on My external HD named as Movie project + date
- then Start FinalCut
- AND set up ALL Scratch disks to this folder
- then SAVE projects - and direct this to same folder
- then I also make a folder in this project folder (on ext.HD) named material - and in this I collect all photos, audio-files (all converted to .aiff - NO .mp3 or other) AND all texts in a text document to copy from e.g. Title, contributors etc. SO also a document describing how the project is to be done - sort of synopsis.
When changing Scratch-disks in FinalCut Express or Pro (FCP-X i don't know) one must when starting up next time - FIRST CONTROL - where they are set - as they do not orient after project but after last settings. All material and Captures etc - can be stored in a very wrong location IF one doesn't keep this in mind !
MY OWN experience - very tedious to clean up - BUT at least FinalCut Pro can help in collecting in all parts if they go astray.
Yours Bengt W