Put the pack on and buckle the belt where the padding in the belt's middle, from bottom to top, covers up the crest of your hip bones. If your straps do not lay flush on your shoulders, front and back, then the torso is too long. Get the harness adjusted to where the belt latches exactly horizontal with the entire shoulder strap contacting the entire surface of the top and back of your shoulders. This puts the lumbar pad in the lumbar area of your body. Keeping it from riding too low on your spine and causing injury. If there isn't enough frame length for your height after doing this, then you had better send it back and get a taller frame fro Kifaru. No sense in not doing so as you could have bought a $50 dollar pack and got that. Instead of a $650 pack.
Do all the adjusting with load lifters loose. To ensure you have a proper fit after achieving complete shoulder and strap contact, with the belt latched horizontally encompassing your pelvic crest crest, which places the lumbar pad in your lumbar, load it up with 30-40 pounds and, engage the load lifters. Have someone put their fingers under the straps on the back of the upper delt's. With that amount of weight, it shouldn't take much load lifter engagement to be able to release the pressure from that area on your shoulders. Just snug them. If they don't relieve the pressure enough for your helper to wiggle their fingers under the shoulder straps, your frame is too short.
The thing about packs is getting the belt where it belongs. By ensuring that you make the shoulder suspension length fit with the lumbar pad where it belongs, you won't have the slippage problems people complain about. Your shoulders are going to carry some weight. There is no way around that. So, proper pack fit is simply ensuring what weight they are carrying, is distributed to the front delt's and chest where it belongs on those heavy loads. Good luck and God Bless
