I don't understand how you EMG users have such weak signals. If I turn my input over 20% I start getting a bunch of red lights. 81/85 in a Steinberger ST-2FPA.
Set it for your hottest guitar and forget it.
It has NOTHING to do with input level. It sets the A/D levels. Signal path and amp gain are not effected in any way. You can set input trim on your specific presets in the amp block.