I have always used the combination of pack frame with a day pack and other gear tied on for carrying in. I got a Sitka 45 last fall, but it came too late for me to test out west. My first gut feeling is that, yes it is narrow and may lend for easy movement through timber, but when fully loaded with gear it seemed like the volume would increase upward. I'm not sure I would like that. It is well constructed and fits nice, although I'm not sure if it comes in different lengths to fit longer or shorter torso. I am on the Sitka pro staff and I am honest in my assessments. The outter shell is watter resistant which is an advatage for me since I carry camera equipment, however it was slightly more noisy than the wool shell of my Bison Gear Elk Hunter. I guess what I'm saying is, for a complete pack that can be used to pack in your camp, it will work great. But to second as a hunting day pack in thick cover or to be used as a whitetail pack for carring my stuff into a cold weather treestand, it may lack the quietness I have been accustomed to. As for Sitka Gear, these guys are very attentive and may have already started to correct some of the minor issues for the new line. It's a fast growing company and they are still making adjustments. If you try something and its not as expected, they have a great warranty and return policy.
Mike