Thanks to everyone. It seems to be working in Left4dead2 with sm2870 and mm688. 8 player coop up and running, can join through browser or steamgroups. Will report back if I have any problems but everything appears ok now.
Had to delete the mod - reinstall mm and sm, compile the sources and everything is fine now. Removed sv_removehumanlimit 1
and sv_force_unreserved 1 from cfg files as they appear to be for the L4Dtoolz version. No errors in log files and Left 4 Downtown extensions , bebop and l4d2 Remove Lobby Reservations plugins all show ok.
Thanks again!
