since i moved from 2 to 4 tables at once i noticed that my swings really appear to be widened somewhat. so what might have rattled me somewhat at 2 tables might be standard fare at 4 tables (i.e. 8 buyin swings on 2 tables isn't as easy to swallow as it is on 4 tables). accordingly, i have come to find that i find myself preferring a slightly larger bankroll than i once did. but not by too much, maybe on the order of 15% or something along those lines, certainly not doubling up. if you're playing solid poker, 4 tables will grow your bankroll, not shrink it.