The Kifaru ultralight is not a pack but rather a frame that you attach a bag to. So the Timberline 3 bag will fit on the ultralight frame. Or you could get the hunting frame but the only difference between the hunting frame and the ultralight frame is the stay supports. The hunting frame has composite stays while the ultralight frame has arrow shafts. You can interchange the stays if you so desire. Hope this is helpful. Fatrascal.
I have a Timberline (not sure which one?) and really like it for hunting. I believe the Timberlines are 4000ish CU so aren't overly big. If I'm going to be packing super bulky loads I switch over to my EMRII. The EMRII is great for hauling lifesized capes plus camp and large quarters of elk and moose. If going to Alaska for sheep or goat I bring my EMRII and for day hunting elk or other species here in Colo I'll replace it with my Timberline. There are really nice outer pockets on the Timberline with quick and easy access to gear. I would highly recommend a guide lid for storing your rain jacket and other quick to get gear.
Another tip is to wear your Timberline plus frame as a carry-on in the plane. You can likely pack around 60 lbs of gear that will save $ for baggage. I usually carry my pack plus a super big camera case that holds my spotting scope, binos, camera, etc. on the plane. It's a pain carrying 80 lbs around the airport but saves $!