Single-camera slowmo cutaways in FCPX

So you want to replace a bit of hasty panning with slow-motion of the cutaway angle?
Keeping the audio track intact and using a bit of classy motion flow, eh?

But you've got FCPX ... so instead you're getting ...

1. Stabilisation refusing to turn on — you were wanting to use that, right?
2. Audio timeline collapsing when you don't want it

The trick is to do everything in this order:

Cut Primary ⇨ Stabilise ⇨ Delete Audio ⇨ Fill Audio ⇨ Trim Cutaway

1.  Go blade cutting at the maximum extent of your primary angle.

     (worry about trimming the cutaway footage later)

2.  Turn on Stabilisation for cutaway angle.

     FCPX won't allow dominant motion analysis after step 3:

     If you delete your audio track first, a bug prevents DMA.

3.  Separate, then split off audio track of cutaway angle.

4.  Delete cutaway audio;  then extend (de-trim) previous audio track.

     Extend it to the start of the next audio track.

     This provides a reliable anchor in the new FCPX paradigm.

5.  Temporarily disable Stabilisation if required.

6.  Now apply re-speed and trim your cutaway angle.  Rinse & repeat.
     Using opt-[ and opt-] is generally the most fun way to go about trimming.
     The de-trimmed audio track will keep a hold of your endpoint.

7.  Turn on Motion Flow and reactivate Stabilisation as necessary.

Interestingly ... you may find that Motion Flow does a better job at Stabilising

all by itself.  After all, a wobbly camera is less wobbly at 25% rate.  I've never

seen a handheld video at 240fps that looks like it needs a tripod or steadicam.