Try a 80hz crossover. Set the volume knob so you are at 75db at the left main speaker and calibrate clockwise(L/C/R/RS/LS etc.). It's possible due to equipment placement, sensitivity and room effects that you may end up with those trim levels being as far apart from each other as they are.

In the end, if it sounds good, don't worry about trim levels. They're there to give you that adjustment.