[i][I'm gonna have to start putting this answer in my signature lol][/i]
I currently tune Drop C Standard for my band FSOF and use string gauges 45-105, with similar tension and action to standard tuning.
It's as much (if not more) to do with the core thickness, thicker core, more tension!
Try giving Malcolm at Newtone Strings a call, tell him your preferred gauge (what you find comfortable), the tuning you wish to use, and he'll sort you out a tension that works best!
Oh and they cost no more than a set of Elite/Rotos
Si