Channel Offset, MMAP

[audiofool]

Testing NAA on a cubox.  I am using a cheap 4 channel dac on my desktop UMC404HD.  Direct connected to computer I can set Channel offset to 2.  This allows the rear channels to avoid the mix controls on the dac.  When using NAA the option is greyed out.  The work around is to map channels 1 and 2 to 3 and 4 - this doubles the network traffic and shouldn't be needed.  I have tried a custom asound.conf to map the channels but networkaudiod seems to ignore asound.conf.  Any ideas?  Sorry wrong place - reposted in NAA