7.1 audio calibration has 5/6 as rear left/right for me, and 7/8 as surround left/right, rear is back, obviously, and surround is side.
This is the proper order of channels for Windows Audio, back before sides.
You can confirm with a 7.1 channel position clip to check if all comes out the right channels, with this for example:
http://files.1f0.de/samples/Surround_TrueHD_7.1.mkvIf the channel mapping is wrong, the airplane movement sounds rather weird - if its right, it should sound like its flying around you.