The main tuning i use in my band is Drop C Standard, so thats C, F, Bb, Eb.
I use 45-105 gauge, high tension, Newtone strings and get a tension and action similar to a bass tuned to standard.
Although gauge has a little to do with tension, the perception that heavier gauge is necessary for lower tunings isn't precisely true, its more to do with the size of the core of the string. The larger the core itself the more tension you get, giving the potential to have lighter gauges in low tunings. Thats if you can find a string brand that can custom wind thicker cores to the gauge of your choice, like i said, i use Newtones!
Si