Never. I have worked with probably a hundred sound guys or more. Never ever did one touch any personal backline gear.
That being said, for bass frequencies, I can accentuate from behind the board. If you send me virtually no mids or highs, I'm hosed. So, for a professional sound guy anyway, if he says he needs more mods or highs, just give them to him. FOH is way more important than having your favorite rehearsal room tone on stage.
And, no, don't hit me with "A good sound guy can make any bass tone fit in a mix". BS. If you think that you don't understand acoustics and/or physics at all.
Either way, that doesn't justify EVER touching your gear.....ever. I'll let you sound like crap before I touch your gear.