Credit to TriCEVEN ,

This will help you play with friends, but the only thing you can change is Time Limit.

Step 1 Goto the main screen and press start, You will be brought to the "quit demo, options, xboxlive" options screen. STAY IN THIS SCREEN

Step 2 Get a friend to send you a game invite(any game will do).

Step 3 Accept the invite, then when it ask if you want to exit your current game hit no. You will now be brought to a screen where you can change to private match and invite friends.

DO NOT EDIT: Game Mode or Frag Limit It Will Crash the Demo

I guess we can strech out some real matchs now huh? :)

Zipkick on!