I like my bottle cages on my Julianna.
Just saw your post. I ride a Julianna and almost never use a camelbak, I just don't like the way they feel. I use both bottle holders, the one on the bottom is where I keep the bottle I'm not currently drinking, either the full one or the empty one. When the top one is empty I switch the two and wipe off the one that was on the bottom. Works great for me. I did an endurance event Saturday and was very happy to not carry a camelbak for close to 9 hours. Most of the front of the pack people didn't. I carry my tire changing essentials in an under the seat pack and anything else I need in my shirt pockets.
Still looking for a bottle solution too . . .
I just found this thread by "googling" the same problem - I just got a new Superlight (same design as the Juliana) and found the "small" size only has room for the bottle at the VERY bottom :( I really don't want to use a hydration pack if I don't have to. Also, I like to take liquids other than water, which I understand you can't use in the hydration pack. I am interested in that behind-the-seat bottle holder if it comes in a small, single-bottle version, as the dual type would prevent adequate "clearance" to descend properly (as someone already mentioned). Hmmm . . .
Happy but Thirsty