My very first pack (after the dreaded Alice pack of the early 90's) was a Mountain Smith/Kifaru in 1997ish, had different kifaru packs, then tried KUIU and we did not jive AT ALL! Back to Kifaru Until 2-3 years ago and tried a Stone for a spring/summer and it hurt my hips, at the same time I tried a K3 as the K4 had just come out and the hip belt SUCKED on me. Now I have had the K4 for a few months and to me the frame fits and carries like a Kifaru with a much better (and lighter) bag layout, IMO a little better belt too. I did swap all the buckles to Kifaru buckles as they are stout AF..
All that being said, as grand master so kindly pointed out, I am build like a Neanderthal and have great booty so that probably played into why I could get along with the other packs.
Most guys built like you lean K4 or Stone... no clue about the AI.