You can create happiness for the musicians onstage by using what already exists in your environment. Before deciding where to set stage levels, listen to the P.A., the room's characteristics or the amount of lower frequencies that spill out the back of the subs and onto the stage. The FOH systems engineer may back up the left and right or the subs alone. This is stealing some of what's used out of the house system to use for feel and air movement onstage. I think of what can happen to create level spikes. I always have pads out on mics and channels. If a pad gets bumped or fails, the input lowers as opposed to raising 15 dB or so. A good hard-knee peak stop limiter or the legendary Aphex units in-line can save a person's hearing and your job.