I love TalkBass forums. The thought of B-E-A-D occurred to me this morning, so I searched it here and voila. You guys are the bomb. It appears that there are 2 different methods discussed above; tuning down, or actually buying a thicker B string (probably in a typical 5-string pack). Obviously tuning down would be easier and cheaper, but surely that would screw up the neck in some way, right? Enlighten me, please.
Well, first time I tried BEAD, I used a five-string set, filed nut, etc. Figured neck tension would be about the same. After a bit of that (and an uptune to Db for about a week) my neck was all kinds of twisted.
I downtuned on another one later with .110 gauge strings and it worked out okay for me. Strings were rather loose, but that's all I noticed. You might want to lower neck relief some for the lower tension though.