i've wondered about this myself. i could get over the playability thang pretty easily, but i don't want to hurt my bass. i may be joining a band that tunes their guitars down a whole step, then the low D down again to C, yielding a C-G-C-F-A-D tuning... so i was looking into tuning a bass C-G-C-F. this would obviously call for custom gauges (probably .125 - .90 - .70 - .50, or something) and a set-up, but if done correctly, it shouldn't be to big an issue, right? i mean, the GHS Zakk Wylde set of 10s for guitar goes (high-to-low) .10 - .13 - .17 - .36 - .46 - .60, or something... so the "off-balance" string tension thing isnt' completely unheard of.....
but then i just figured i'll do something like C - E - A - D or C - F - Bb - Eb. or maybe just B - E - A - D and call it a day.
but yeah, if the set-up is done correctly, would something weird like C - G - C - F be detrimental to the health of my bass's neck?
