How to sync mixed audio into FCPX

After the cut is locked, I export a fcpxml of the project, then run X2Pro to create a ProTools Session. (See: http://humanuser.blogspot.com/2016/04/fcpx-to-protools-via-x2pro-ironing-out.html)

Mixing is done into ProTools, and a 4 tracks mix (Stereo Dialog stem/ Stereo Music stem) is Bounced out of ProTools to sync back into FCPX.

In the Timeline, select the original Music and click (V) to mute it.  Select all the video clips, and then "Expand Audio Components" (Control+S), then select the audio portion only of the clips and click (V) to mute the audio only.

Now all your audio is muted. Collapse Audio/Video (Control S.)

Import your mixed stems, make sure to select the proper Pan Mode - stereo in this case, and sync them to the In-point. Done, now your final image plays with your final mix, ready for Share / Export.