I have found that though the HPG kit bag is nice, it is much more comfortable when wearing a small backpack to balance out the weight. So in the small backpack, (I use the REI Flash 22), I can carry the stuff that wouldn't fit into the HPG bag.

HPG bag:
-medical kit with tourniquet
-fire starters
-headlamp
-knife, (mora knife attached on the bottom outside straps)
-nav, compass, map, Garmin in reach
-Space bevy sack
-water purifier drops or tablets
-Radio
-Hearing pro/eye pro
-granola bars
-G45

In the REI Flash 22:
-Extra clothes (jacket for rain, warmth, socks, gloves hat depending on time of year and place)
-Water bottle
-other food
-Small closed cell foam pad
-extra mag

"Going to the mountains is going home" - John Muir

"It is very expensive to give bad medical care to poor people in a rich country" -Paul Farmer

"Pain: The gift nobody wants" -Paul Brand