I've been using Elixir Nano's on my SR505 from day one and they're perfect. Great feel, perfect tension (the low B is SOLID) and they sound great.
It's amazing how well a set of strings will work so well on one bass, but not so well on another. I tried using Nanoweb's on my AM STD 5 string Jazz bass and the overall feel was too loose. Played with the action for a while, tried re-positioning my plucking hand but it just wasn't happening. Too bad because they sounded great.