first off i tried xy pair and tried to get a balance of guitar of vocal buy adjusting height.
Didn't like it though, it sounded holy in the middle (as it would) so i did spaced pair next.
That sounded way better, but pete moves his head about sometimes, and the voice would travel left to right in the mix which i find really offputting.
So i stuck the sm81 in the middle of the pair at the same height and distance as the others, but aimed it up the ways (pointing at his forehead or thereabouts)
i rolled off below 100hz on the 81, and when i bring its fader up and down, it just naturally brings up or down the voice with little effect on the guitar

hope that's useful.