Played a great round of rush just a while ago, the map was Port Valdez and I was on the defending team. It started out as a 12vs12 match and about halfway through there were only 4 players left on each team. There was much more suspense since you couldn't afford to die and luckily everyone didn't play the recon class. The attackers didn't lose tickets as fast as they usually do in a crowded game, so we played for quite a while. Both teams were fairly even in terms of skill, but eventually the attackers got the advantage when we couldn't destroy their tank before it got into our base.
The fact that there were so few of us on each team also meant that we really had to work together in order to survive.