i have used 100's as my thickest string, GHS boomers and gone down to Low C tuning on all strings. i cant imagine a 4 string going down to B without some serious problems such as strings frettingout, intonation problems.
i guess you could just try it, but thats pretty much why they made 5 strings for.
saddle, neck, intonation adjustments would be needed for either tunings to keep the thing in perfect tune, but if all you play is from the 7 fret up you may not need to.