Have each player arrange their character sheets so that they're in a line, w/ one clearly in front, another bringing up the rear, and the other(s) in the middle.
I'd rule a maximum of 8 zeroes could attack a medium sized adversary, if conditions were right. For larger opponents, allow more as you see fit, but I say just let 'em all take a whack at it if they're brave enough.
This is essentially using character sheets as miniatures on a square grid mapboard, whereby the four facing (front, back, left right) and four diagonal can all get in a swipe. Works best for dungeon crawls and inside buildings where everything is square.
If I get into a situation where there is a huge open space, often I'll switch to a hex grid mapboard because it allows for more normal movement (diagonals usually are 1.414 greater distance than non-diagonals) and limits the number of opponents to six rather than eight.
_________________Marv / FinarvynDCC Minister of Propaganda
; Deputized 6/8/11
DCC RPG playtester 2011, C&C
since 2003, ADRP
Since 1993, OD&D
player since 1975
"The worthy GM never purposely kills players' PCs, He presents opportunities for the rash and unthinking players to do that all on their own."
-- Gary Gygax
"Don't ask me what you need to hit. Just roll the die and I will let you know!"
-- Dave Arneson