Yeah, my strategy changed dramatically the other day. We used to hold up in the fire pit room, and the farthest we got with 4 people was 19. Now I've completely thrown the defensive location tactic in the wind, and have went to a "flight" method. Basically, make as much money as you can using knives through the first three rounds, go upstairs, open the two doors and buy the pump shotgun. Defend that room until you have enough money to open the door to the dressing room and also the one leading to the stage. Turn the power on, link the teleporter. You will make the zombies "train" if you stay going in this same loop in the order that you opened doors. When the round ends, wait in teleporter and fight off zombies until they are about to overtake you. Then teleport to projection room and start chucking grenades in a dispersed pattern (you can go to the wall and buy more, usually get 3 volleys in). You'll be teleported back to the lobby and you'll hold it as long as you can, then start your loop again. If you didn't chuck all your grenades in the same spot, you should have a good collection of crawlers in the theater, which will give you time to sync the teleporter (your priority) and rebuid the barriers, hit the box, buy drinks, etc... At the end of round go back to the teleporter again and repeat. I got to level 19 the only time I've tried it solo, and would have probably made it farther if I hadn't had people start texting me while I was in the thick of fighting. This is kind of a hard techinque to use if you're in a larger group as everyone has to be disciplined; tight group movement (if you split, the zombies will split direction), no fretting over the box (there will be plenty of time), don't try to wade back into the horde to pick up anything, and downed people are SOL until next round (unless they survive until the group makes the loop).