Since it's an AI tournament, you may want to make the challenge be the brains of the machine instead of the body. One programmer should create the entire robot as well as the interface. The role of the contestant ought to be to make an algorithm to coordinate those functions. This way there's consistency in the physics and rules of the robot, and you won't have to screen every submission for cheaters.

SUMMARY: Make fully functional robot & arena but with no brain. Let contestants script a function to coordinate robot's pre-made actions. Then the contest tells who makes the best A.I, not the best robot.

Actually, since everyone on Newgrounds plays it off the same uploaded file, that would bloat it to way beyond 800 KB. Assuming you're using Windows, the shared objects are located in

C:\Documents and Settings\[Your profile name here]\Application Data\Macromedia\Flash Player\...

Beyond that it's dependant on what you've done with your computer. The easiest way is to run a search on your computer for gamedata.sol. All your data is stored in the same folder as that file.