Technically the best way to set levels on the M10 (or any other recorder) is to switch on the mixpre's tone generator and adjust rec level on the M10 until it registers -20dBFS. From memory on my unit that was at about 4.5. This way you'll know that the mixpre's clip level aligns perfectly with the M10's clip level, and you can now just watch the mixpre meters and not worry about the M10.
Pan switches should always be set hard left and hard right, otherwise you won't be recording proper stereo. Turn on the fancy new ch1-2 gain linking and you're good to go! Wish I still had a mixpre
Ben
I checked the tone generator and my M10 can be set to near 5 (approx 4.8 ). Setting it to 4 (which is unity gain, sets it to about -23db). There is no way the M10 is gonna record incoming signals to loud (overloading). But.....is this setting not a bit too safe? (I can normalize it ofcourse, but aren't you missing to much setting it this low?). I did my first concert last week, where I ended up setting the M10 to 7. No overload, no nothing and still plenty headroom to normalize it.
Second, what you mean by "turn on the fancy new ch1-2 gain" (is that the Limiter switch setting, setting to LINK?)
Edit: This is what it looks like (for those interested), remember, the small levelknob on the right is set to approx. 4.8 )