Hey man, I don't know Mark Morton's exact settings, however, I have a Mark IV set up right now that I think is getting an amazing LOG sound, you can hear for yourself here in my youtube video:
http://www.youtube.com/watch?v=BKoc7QB65QI
I even took a picture of my Mark IV settings, instead of typing them out, and I always have a hard time explaining the active EQ settings, figured it was easier to just take a pic and let you see for yourself. Mind you I am using active EMG 81's, so I have the head set accordingly, depending on your pickups and such you may need to tweak a bit. But let me know what you think of the video, and if this works for ya!
I am in Tweed Power, Lead Gain and Lead Presence are OUT and the drive is IN. Im running the switches Mid Gain, Class A, and Pentode. Give it a shot and let me know how it works for ya, I can't seem to get enough of this tone. Cheers bud.