I know this is an old post but this is what I created with a military pack. I used the pack in the picture by itself in Wyoming last year and it worked great.
For My Idaho Elk trip this fall I am attaching an Eberlestock
scabbard onto the pack using the molle system. I still have to test it to see how the scabbard works on the rear of the pack, instead of behind the frame like the eberlestock packs. I still have one strap to attach around the top so the top of the scabbard doesn't pull away from body.