@ Leigh
The small silnylon pack I mentioned was much like the Hipster and best used the same way that Gossamer Gear reccomends, as a "belly pack" over the top of a backpack waist belt. The Hipster uses PU coated nylon which is tougher and can handle objects with rough edges better.
I think these smaller sub-2oz pocket sized models may be a good alternative to the neck lanyard debate, for carrying critical essentials.
I've done the dance of paring up a hydration-oriented lumbar pack with a SUL backpack. It makes sense to carry the greater water weight on the hips and carrying water is usually the challenge with most packs in the "stuff sack with shoulder straps" class. While the combination is practical enough in use, you can get packs with water bottle pockets and more capacity for less weight than a hydration lumbar pack plus SUL day pack.
it seems that hydration-oriented lumbar packs get caught in a design death-spiral, adding more padding and wider belts to keep it in the lumbar area and adding more stabilization straps and associated hardware to keep it from bouncing. Many designers do a nosedive off the ultralight bandwagon, adding more compression and lash straps as well as layers of pockets and organizer panels, and using heavy fabrics. It's not a bit different than backpack design, adding features and weight. Mountainsmith has taken it to the point that they offer shoulder straps to keep the monster from slipping to your knees when fully loaded.
It would be great to see a lumbar pack that adheres to UL principles and still carry a couple 750ml bottles, a snack, and some core essentials.