Typically we only have one class with a MAXIMUM size of 20 cm by 20 cm. The boebots fit within this. Since the chassis is somewhat smaller then this (about 12cm by 14cm) there is space for "customization" Folks can attach wedges, flip ups etc to the boebot chassis.
The vex bots square bot is too big for this competition. I have seen folks get really creative and make two wheel compact vex bots with a caster that will work.
The complete rules for the competition are at:
There are a couple of pictures of the robots in the minutes from last February.
Here are some pictures of one of the sumo bots I built:
As you can see the boebots are NOT outclassed in the category! Have fun!