I'm not big on ultimatums either but this is worth trying as a means of asserting a say in the mix:
Originally Posted by two fingers
I have only found one solution for this. I have told countless guitarists that they can tell me to turn down the moment they point their amp at THEIR head, not mine! You tell your guitar player to either put his rig on some sort of stand (if it's a head and cab) or tilt it back and point it at HIS head if it's a combo. If he still plays as loud as he did before, the situation is hopeless. Tell him how stupid he is as you pack your gear. See how much he likes it when you are REALLY not there.
By the way, how do the other band mates feel about it? Are they ALL as frightened of the ego maniac guitar player as you seem to be?
IWNBARMPB Prezident, Team Trace Elliot #1, Mediocre Bassist #399, Old Basstard #86, PBBBC #2