I've been wanting to get some roughly .12" ti rod, as long as it's very hard, tough grade, to use for a u frame for a backpack, or, more likely, two L parts that connect on the small top leg of the L, since that allows for shorter shipped ti rod.
I have a Lowe zepton that uses a u frame made out of steel, about 1/8" rod, incredibly strong, and the pack, without top, weighs 2 pounds. Narrow U, about 5".
So it's crossed my mind to do that with titanium as well, since it would be plenty strong and stiff.
A narrower U allows you to make proper wings on hip straps, connected about 6" apart, and to go up to shoulder straps for load lifters, and to arch it out a bit to move the pack body off your back.