older thread, but thought I'd add the Mountain Hardwear Fluid 6 to the mix, this was recommended to one of our fellow BPL'ers
I've been using a couple of different lumbar packs w/ double bottles w/ success, but they are limited to moderate distances- lack of storage for food, insulating layer and the distances you can cover w/o water
I wanted something that could handle longer runs, was light and carried w/ little to no bounce- the Fluid 6 really fit the bill. It weighs in at a very svelte 9.5 oz (that's w/o a bladder which you have to supply- I opted for the lightest 2 liter I could find the Platy Hoser). The main pack is surprisingly roomy- can fit extra clothing, full days worth of food, emergency bits. The front vest portion has several smaller pockets that can handle gels/blocks/electrolytes and other items you might need handy (sunscreen, anti-chafe, etc). The side of the main pack had two elastic pockets that are able to hold your typical 20-ish oz running bottle, but unless your more flexible than me (which most folks are :) ) they couldn't be reached on the fly. They are a nice size to hold a cell phone, camera, etc though. The front of the pack has a full length bungee setup that allows additional items (raingear, etc) to be strapped on.
I haven't tried it, but it looks like you might be able to carry two bottles on the front of the vest, there are two smaller double bungees and it looks like the bottom of the bottles would fit into the stretch pockets
the adjustments are two sternum straps that can be moved to several different locations on the "vest" and two easily to reach straps where the lower portion of the "vest" is attached to the pack
I've got several 20-ish mile trail runs w/ this pack and can say it carries very nicely- this is my first vest style running pack and now I know why they are so popular.
I do wish they had one additional mesh pocket in the main pack to store items like tp, first aid, headlamp, etc- right now I'm just using a very small cuben bag to store the smaller items
on the job :)