In general you have to open up the court and take the game away from the basket. On offense, teach your players in the attack zone to attack the bigger man off the dribble attempting to get by them to the basket and draw the second post or another help defender. This almost always opens up additional scoring chances for your team. A small team afraid to attack the bigger men is like a shoe without a foot to cover. Develop your teams explosive quickness in jumping and more importantly to the ball.
Many small teams have some quickness but play lethargically.
Explode to areas, take away the defenses reaction time to situations and force their big guys to move their feet as much as possible. I highly recommend Donald Chu's book or video on Plyometrics found in our Sysko's portion of The Hoopstore . It has been my experience that at the highest levels the ONLY way for small players to succeed at the game is to have developed very finely tuned fundamentals and take them to the level of fully automated skills. They must be able to pivot and pass in traffic with either hand, penetrate and pull up for the J. Play with balance and control. If my team were small I would be very focused on refining many of their skills beyond what is normal for their age level.