THE RECENT UPDATES/PATCHES FOR L4D FROM STEAM/VALVE HAVE BROKEN THE MULTI-SLOT MOD FROM ALLIED MODDERS. 
THE ONE I WAS USING WAS QUITE OLD. 
AND OF COURSE WHEN I ASKED VALVE ABOUT IT, THE REPLY WAS BASICALLY : YOU'RE S.O.L. SOMETHING ABOUT LEGACY GAMES, BLAH,BLAH. 
BUT AS WE KNOW, VALVE CAN'T COUNT PAST 2.
AND STRANGE THEIR STILL SELLING L4D, BUT WHILE THEIR STILL MAKING $$$$$$ OFF OF IT, THEY DON'T WANT TO FIX IT, IN ANY WAY.
I NEED A MULTI-SLOT MOD, AS I HOST 2 SERVERS AND HAVE A LOT OF FRIENDS WHO WANT TO PLAY TOGETHER, MORE THAN 4 AT A TIME,  L4D
THANK YOU