I'm another Mountainsmith fan. I have three Day, one Tour and 12 Vibe II's (long story...). The Strappettes really make the larger packs!
I'm not too far behind on the Vibe II's - we have six. One for each member of the family in different colors and 1 extra. In our family we also have have two Tours, a Swift II, and a Clear Creek 20 backpack. We're big fans of their products.
The Strappettes really make a huge difference with the larger lumbar packs. I recommend them too.