A client showed up a while back with 3mm thick cork pads under his bass' bridge feet. His strings had gotten too low so he had fitted these pads; also he claimed the bass sounded better with the cork there. Surprisingly, when the cork was removed (and replaced with well-fitted maple) the bass seemed to lose power and tonal complexity. I was dumbfounded, and put the cork pieces back. I can't explain why.
Frank Tate uses cork under his Hawkes' bridge and swears by it. I didn't hear his bass without it, but it sounded great with it.