I saw last saw Martin around a year ago, and wile I was talking to him and a mutual friend, he was busy putting a set of D'Addarios on his guitar. I didn't ask about gauges, but I do know that, as Some Bloke says, he uses heavy bottoms and lighter tops.

With regard to tunings, get hold of his CDs - I'm sure Martin will appreciate that - the tunings are given in the notes.