I think the lack of responses may be due to this being the incorrect location for technical setup questions.
Settings to get the AVR to do the most-minimal volume correction possible could vary greatly depending on distance from the mains, subwoofer placement within the room, and numerous other variables.
I do not suggest cranking the sub volume at 100% and letting it go from there, because the AVR will end up over-reducing the signal voltage going to the sub. This is not necessarily good... The same thing would happen if you turned the sub volume to 10% and let the AVR attempt to fix it likewise. Over-amplification of the sub channel possibly to the point of clipping or exceeding the subwoofer inputs.
Since I am familiar with the MCACC routine (vsx-1021 owner), my suggestion would be to toss it in with sub volume at 50%, phase at 0, and freq at max, and run MCACC. Then review the volume adjustments in Adv MCACC that it attributed to the sub channel. You are shooing for the least AVR correction possible.
Example: You run it and it applies a -3db to the sub, turn the sub volume down 15% and re-run.
Example: You run it and it applies a +3db to the sub, turn the sub volume up 15% and re-run.
Example: You run it and it applies a +0db to the sub, play the lottery, come home, crack a cold one and toss in a movie!