How to work with Multichannel tracks, "on the road", and downmix from PTHD12.4

Hi guys !
Sorry to disturb you with that, but I really need some help ;
I just bought a PTHD12 (from a complete production toolkit crossgrade) ;
I bought an HD version to manage Surround Track (4.0 or 5.1) from my laptop with internal card, on the road ;

I wanted to do pan and premix all my tracks in 4.0, setting them, making to stereo output (LR and LsRs), to do a lot of work outside my studio ;

Actually I don't understand, because I can't create a quad output or quad track, setting both output (LR or LsRs) on my soundcard (internal mac soundcard) ;

Do you know how could I do this ?

Thanks,

Cheers,

Joss

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How to work with Multichannel tracks, "on the road", and downmix from PTHD12.4