I did a quick search and did not see it posted up yet but Kifaru has just released, as of yesterday, several upgrades to their existing packs as well as some new items. They are calling the new line "G2".
The most interesting new products are their "Armor Grip" packs (AG1 and AG2).
http://kifaru.net/AG_1.html (Based on the Navigator)
http://kifaru.net/AG_2.html (Based on the EMR)
They are designed to mold around the rear plate to form a stable platform and not shift around.
I have not tried them out but it looks like it would work well from the pictures. I know there are quite a few Kifaru fans on here.
Enjoy.