+2 on checking out the SMD Starlite. With the "optional" (mandatory, IMHO) stays it will support at least 35 lbs. comfortably. And it's plenty roomy (too big for me). It's a pound lighter than the ULA Catalyst.
I have the Starlite's discontinued "little brother," the SMD Comet. I've carried up to 37 lbs. in it with no problems in shoulders, back, hips (although my knees and feet were screaming and I'll never do it again). And even the smaller (2400 cubic inches in main body) Comet takes a bear canister sideways.
If you don't yet have the packraft or the bear canister (I assume that's why you can't measure weight or volume?), I strongly recommend you get those before getting a pack. That way you can be sure the pack will fit your gear while it's still returnable!