Is there a difference when using the L/R channels as opposed to the numbered channels? The manual says these are stereo. Is there a way to force them to record mono? I'd really like to use the backup recording feature (where it creates a second audio file at -12db). I'm using this mainly for weddings.

Would it be safe to use either the L/R for wireless mics or a connection to the soundboard? Will the audio come out okay or will I have to level the left and right channels in post?

Thanks!

Channels 1 - 4 are all enabled as individual (mono) channels by default, however it is possible to pair them as stereo channels (see manual p.26)
• If you press track button 2 while pressing and holding track button 1, tracks 1/2 will become a stereo track (stereo link). Tracks 3/4 can be made into a stereo track in the same way.
Stereo links can also be deactivated in the same way. The L/ R track stereo link, however, cannot be deactivated.

However, what that doesn't tell you is that when using the optional plug-in XLR/TRS module on the L/R channels, they behave in exactly the same way, as unlike the X/Y, the M/S and the shotgun mic modules, there are separate gain controls for each channel on the XLR/TRS module. I've been using the L/R inputs to record from audio mixers so that I have the -12 dB backup available if necessary.
I have also used a TRS +4 dB line output from a mixer on the L input (20 dB pad required) while having a radio mic receiver on the R input, giving me a backup for both.

But as I said, you will need the optional XLR/TRS module for that - you can't separate the L & R channels when using the 3.5mm jack input on the X/Y mic module.

Just remember, no phantom power is available with the plug-in XLR/TRS module but that's not a problem with how you want to use the H6.

Ah great thanks! I will pick up the extra XLR module.

Glad you found that helpful.
You might like to have a look at http://www.dvinfo.net/forum/all-things-audio/521756-whats-your-kit-list-attach-various-sound-desks-your-cams-xlr-input.html as well if you haven't already. Just as useful for connecting to an audio recorder like the H6.