Yep,
I am old, tired and still on N7 
OK…is there a way to export interleaved multi channel mix in 1 go ??? Say 6 stereo stems ( not surround ).
Not sure I understand the question.
Stems are per definition not a “mix”.
So, are you trying to export a 5.1 mix into 3 stereo files (Absolutely no standard procedure) or do you want to export the stems (MX, DX, FX, etc …) of a mix in one go?
Fredo
No Fredo, I wasn’t clear enough sorry. Yes mix in one go, into a non surround interleaved file.
I am mixing into multiple stereo group outputs. My client does not want these individual mixed files, they’re asking for a single interleaved wave file.
Yes I know it is easy in the case of standard 5.1, but these individual mixed stereo tracks will stay as is and sent out to foreign markets .
I am hoping it makes more sense now… 
Well surely you should be able to just send/output the relevant stereo files into a 5.1 output and pan the channels according to taste, no?
I can’t think of a format that would be “convenient” though so I don’t really get why your client wants that, but whatever. If they can’t point to an established format or a channel layout of their choice then just route as you see fit into a wider output and render that…
Or am I too missing something?
Thanx Gents…
I was confused as well, that is why posted. I called them…They want the files in a QT container…I think that is possible. Or…I will download Wave Agent…and combine tracks.