5.1 stems from post production mixer - what is the proper pan mode?

I imported the final 5.1 mix delivered to me from the post house, the come into fcpx 10.3.4 as individual mono files: L,R,C,Ls,Rs,Lfe - I believe I should leave the pan mode set to none for each of those files, correct? I f I set it to basic surround I think I will be messing up the surround balance already set my the mixer and baked into these stems. Is that correct?

Are they playing back properly on your 5.1 audio monitors?

I don't have a 5.1 setup in my editing room, so I'm burning a BD--R disc to playback in my living room home theater 5.1 setup for checking.

support.apple.com/en-us/HT204261

Here is how you do proper multichannel export.
The key detail is the +3db level adjustment.

Do a test on a reference -20db audio stem and you will see if it's correct.

You have to do multichannel export with roles if you want to preserve a surround layout different to what FCPX uses which is from memory is LCRLsLsRs

You can export 16 channels of audio if you setup correctly. I suggest saving a 16 track or 8 track roles preset on th export page because it gets tedious manuallly assigning each time.

If you burn a bluray disc out of FCPX, then you need to use the surround audio configuration on the file. Otherwise the channel layout will most likely be incorrect. On delivering to your broadcaster or distributor, you need to use the Multichannel role output method. As long as the channels line up how they want then it's fine. You can check the resulting file by dragging it back into FCPX and seeing which waveforms show up on which channels. And soloing or muting the channels so you can hear the individual tracks.