It's not strings 6-3, but I've always had a little difficulty palm muting the 1st and 2nd strings. As my hand moves down the bridge my pinky starts to hit the volume knob and I can't get my palm to mute the 1st and 2nd strings like the way I can on, say, an LP or Tele. So to compensate I either, a) Turn or rotate my hand upward, which makes for awkward picking. b) Put the pinky up and over the volume knob, But the vol knob can move and it's hard to get out of that position if I need to get back to the 6th string in a hurry so I usually don't do that. c) Don't palm mute and just lightly pick to achieve the same dynamic. So for those that share in this struggle, what do you do to compensate? Suggestions more than welcome.