Greg,
I also was looking at the Atlas Athlete, with available retro Adventure waist belt for added waist comfort under load. I have the fstop Loka which works "okay" for me, but I also have that svelte figure that Matt brags about
, and I also don't have much of a butt to help hang that waist belt under heavier loads. It appears from the provided dimensions that the Athlete is slightly too small for a technical camera, such as my Cambo WRS1600, unless you break it down and lay it flat. I like to keep my Cambo intact when hiking, well supported and packed, to enable quick set up and shooting. I spoke with Andy Lerman (also a member of Dante's Inferno/Purgatory) and he confirmed that the Athlete was too narrow for a technical camera unless I laid the camera body flat. The Adventure model would work but is a bit too big for what I need.
I have since ordered the Mindshift Backlight from Thinktankphoto. This back has a more generously padded waistbelt and provides needed support. There are three sizes available. My neighbor has the 26L so I was able to try it own and experiment with the Cambo gear. Turned on its side, the Cambo fits in the 26L perfectly and is just big enough to hold my technical camera gear and filters, with ample pockets for food, accessories, etc. The 36L would definitely give more room for gear and probably a better choice for you carrying more gear.
The Mindshift comes in soon. If all works out, I'll probably sell my Fstop Loka with two small ICUs.
Ken