would this work as a mono headphone out?


Well, I think you'd need a stereo to mono adapter for that to work. Otherwise the sound would only come out of 1 ear...

http://www.showmecables.com/product/3-5mm-Stereo-Jack-to-3-5mm-Mono-Plug.aspx?utm_source=google&utm_medium=cse&utm_campaign=957&gclid=CIi3n9WHy8wCFdhahgodrqoFOA


ah, of course :) but in terms of volume levels?


I "think" you should be ok. I know I've used an adapter like that in the past, and simply attenuated an output into headphones, so this should be ok level wise. I'm not 100% sure, but there might eventually be a headphone 1u module from intellijel. I know that they have plans for much more in the format.