This is what i have in server.cfg for 12 slots l4dtoolz
Been working great for years now.
//--> L4DToolZ
sv_maxplayers 12
sv_visiblemaxplayers 12
sv_unlock_sb_add 1
sv_force_unreserved 1 // Force the lobby to be unreserved
sm_cvar survivor_limit 12
And here is superversus cfg
// This file was auto-generated by SourceMod (v1.8.0.592
// ConVars for plugin "l4d_superversus.smx"
// Change Difficulty
// -
// Default: "0"
// Minimum: "0.000000"
// Maximum: "1.000000"
director_auto_difficulty "0"
// Infected spawning rate Multiplier (multi*(survivors-4)). Requires director_auto_difficulty 1
// -
// Default: "0.25"
// Minimum: "0.000000"
// Maximum: "1.000000"
director_ci_multi "0.25"
// SI HP Multiplier (multi*(survivors-4)). Requires director_auto_difficulty 1
// -
// Default: "0.00"
// Minimum: "0.000000"
// Maximum: "1.000000"
director_si_hpmulti "0.00"
// In coop, spawn 1 more SI per extra player? Requires director_auto_difficulty 1
// -
// Default: "1"
// Minimum: "0.000000"
// Maximum: "1.000000"
director_si_more "1"
// Delay in seconds added to z_ghost_delay_max for SI bots spawning in versus
// -
// Default: "5"
director_si_more_delay "5"
// Tanks HP Multiplier (multi*(survivors-4)). Requires director_auto_difficulty 1
// -
// Default: "0.25"
// Minimum: "0.000000"
// Maximum: "1.000000"
director_tank_hpmulti "0.25"
// Once a player connects, 2: Put in random team, 1: Show teammenu, 0: Do nothing
// -
// Default: "2"
// Minimum: "0.000000"
// Maximum: "2.000000"
l4d_autojoin "2"
// Allow extra first aid kits for extra players. 0: No extra kits. 1: one extra kit per player above four
// -
// Default: "1"
// Minimum: "0.000000"
// Maximum: "1.000000"
l4d_extra_first_aid "1"
// Max amount of infected (will not affect bots)
// -
// Default: "4"
// Minimum: "4.000000"
// Maximum: "24.000000"
l4d_infected_limit "12"
// Should we clear Lobby reservation? (For use with Left4DownTown extension ONLY)
// -
// Default: "1"
// Minimum: "0.000000"
// Maximum: "1.000000"
l4d_killreservation "0"
// 3: Enable teammenu & commands, 2: commands only, 1: !infected,!survivor,!join only, 0: Nothing
// -
// Default: "3"
// Minimum: "0.000000"
// Maximum: "4.000000"
l4d_management "2"
// Respawn alive when joining as an extra survivor? 0: No, 1: Yes (first time only)
// -
// Default: "1"
// Minimum: "0.000000"
// Maximum: "1.000000"
l4d_respawn_on_join "1"
// Maximum amount of survivors - (Use 4 to keep bots 4 only)
// -
// Default: "4"
// Minimum: "1.000000"
// Maximum: "24.000000"
l4d_survivor_limit "4"
// If player is afk on versus, 0: Do nothing, 1: Become idle, 2: Become spectator, 3: Kicked
// -
// Default: "1"
// Minimum: "0.000000"
// Maximum: "3.000000"
l4d_versus_afk "1"
// If less infected players than l4d_infected_limit in versus/scavenge, spawn SI bots?
// -
// Default: "1"
// Minimum: "0.000000"
// Maximum: "1.000000"
l4d_versus_si_more "1"