if you go offensive you could design it more compact to go through the lowbar (which is a very strategic component for an alliance), and be able to gather boulders somehow, to shoot in the low goals. If your going more defensive, try a faster and taller robot to block the boulders like
http://imagecache2.allposters.com/im...POD/147605.jpg
as an example, to block shots both on top and bottom, but it can't be top heavy.