Looking at http://equipped.org/devices5.htm, Doug says "This leads to my recommendation that a survival knife should have a blade at least four inches long, but no longer than six inches, or there about." The RSK Mk2 is six inches long.

I haven't had a chance to do much with my Mk2, but it fits my hand well and has good ergonomics. It's probably about as big as I need a knife to be for camping or survival purposes. In the past I've used a full-size Mk1 folder as my primary knife while camping and hiking, and been well-pleased.