If you turn both the left and right 0-20db pads on top of deck on, running XLR (mic in) with gain knob at zero you will get a straight "line in level." We are talking about a level of gain, not the mic in/line in switch. Gain won't be controllable by your deck only by output of SBD. This bypasses the preamps on the deck, which might be prefered over amplifying the SBD signal.
I choose not to run this way as I have to bug the soundguy throughout the show if levels need to be adjusted.
I run XLR from SBD to XLR on P2, mic in, phantom off, pad off, limiter off etc. gain is controlled by knob on deck.