I will add IME, if you want that low loose downtuned tone, you want floppier strings. I just recently found a set of D'addarios that are like 50-120. Its their normal 50-110 with a thicker bottom string. Its perfect for C standard and drop A sharp for me. I tried the bottom 4 of a 5 string set and it was to tight for that loose sound.
My bronco at 30" sounded super evil with its .100 tuned to b.
I think flop and taut both have there merits. taut gives more clanky growl.

