If anyone gets a chance to see Mark live, do it. I have had the privilege to see him play twice and meet him. Last May, he was gracious enough to play at a Lyme disease awareness benefit my wife and I held. Our turnout was abysmal, even for a first year event, but Mark treated it like a full house and played like there was no tomorrow. He was still working out the kinks to Dueling Banjos in a live setting, but did play it. He wasn't too comfortable with it but damn it was awesome. I was able to eventually convince him to close his show with it.
Not only is this man extremely talented, he is truly a wonderful human being. I consider myself extremely fortunate to have met him and consider him my friend!! Even though he doesn't use the double neck, his rendition of Amazing Grace is equally good.
http://www.youtube.com/watch?v=JPtrFyc9KyA