I am running a 26x8x14 Duro Power Grip on the rear and love it. Drawbacks are that it can be dangerous to get mounted and is probably impossible to remove and remount in the field. I have myself convinced that it has such a stiff sidewall that I should be to limp home even with a complete loss of air - although I have never actually tried to do this.
For that type of terrain I would not feel comfortable with a 47 tooth rear sprocket. I am currently running a dual rear sprocket setup with 47 and 55 tooth sprockets and have a 65 tooth sprocket that I plan to install as soon as I get a longer chain.