Lou Dawson's blog WildSnow.com is a great resource for information about backcountry skiing and ski mountaineering. Lou is a keen observer and user of gear and blogs often. Here's his comment about the DownMat 7 on Denali. 

"Louie and I used the Exped Downmat Pump and found that to be plenty. (I should mention that with my old beat up bod, using the comfy 7 centimeter thick Exped was key to my success on this trip.)"

Here's the whole article on WildSnow.com with very helpful hints for climbing/skiing Denali.