I do this often for DCP exports.
New custom sequence, with multichannel mono audio tracks (6 total)
important you choose multichannel and NOT 5.1…for some reason it lowers the audio volume on export.
Then bring in each track in order of smpte specs:
L
R
C
Lfe
Ls
Rs
Then go to the mixer window and pan each track.
L
R
L
R
L
R
Also make sure you check each box (in the mixer) that indicates
L & R is mapped to1 & 2
C & Lfe is mapped to 3 & 4
Ls & Rs is mapped to 5 & 6
(this keeps them all seperated without combining them all)
Export the quicktime, in the audio options choose multichannel 24-bit.
This is what I do and it works. Hopefully i didn’t leave out a step.
You might search more threads in the forum going back, I know I posted
a more detailed version of this some time ago as well as others.