My current home brew rig is the frame of a Kelty-clone, the main pocket of a pattern 82 CF Suplus (with the extra straps/pockets removed), the harness from a different Kelty-clone, and a grid of surplus web straps for general purpose attachment. I’ve also gotten good mileage out of the upper strap set from an 82 for similar builds.
It doesn’t weight much, and carries more than I can.
The biggest problem I’m still wrestling with is that the framing required to do meaningful load transfer to the hips reduces flexibility the rest of the time. It’s hard enough to get up off the ground after a tumble with a heavy pack on, but the the parallel structure attached to the spine makes it worse. Like "Inverted Turtle" worse.
Also, the’ol hips aren’t as well defined as they used to be. Sigh. But that’s not a problem with the pack design.
The US tried to solve the load transfer problem with the ball/socket joint on the back of a semi-rigid belt, but I’ve never handled one that wasn’t broken so I don’t know how well it worked in practice. I have my doubts because I didn’t see a working cantilever mechanism, or rather, a working cantilever mechanism that didn't depend on the user having load carrying abs.
And if you think “It’s military equipment, it must work.” I reference the previously mentioned pattern 82. Yuck.
I suppose on some level I’m chasing a rainbow. Large mass has to be carried high for balance, which means I can’t have stability. To be stable I have to carry it low, which limits mass. I can’t have both.
Not that people won’t try. There’s a wince-inducing training video on YouTube about how to pack a ‘42 mountain pack. Being 20 years younger probably helps delay the impact of that kind of spine-abuse, but you'd still be skiing along bent forward like Igor.
Also, has anyone found a good solution to the "wet-frozen web straps can't be moved through ladder buckles" problem?