when u are in the lobby set up wireshack like this
capture, capture filters, udp, ok.
capture, options,start.
u will c all the packets,,, find any game, leave game
backout to the main menu, unplug ur cable from the back of ur ps3, and plug it in, sign in, and u should be strict, stop the packets.
now u can lock totaly any game,,,, but u can mergue with other games,,,, so the best way to hold the lobby is upload youtube vid, and rapidhare file,,, at lest u need 8-9ppl to start the game(like domination, team deatchmatch), so when u have 8 ppl, leave game, the game will start without u, and its already lock it, now any friend need inv u, and that is it,,,,
Note: the only people that can join your party are the ones you invite, in lobby they can join session.