#1 need to change my center foot wheels system

During the event "facts 2011", i've got some problems with the wheels in my center foot. my first system wasn't very sophisticated, long threaded rods between the JAG Center Foot Caster Brackets and a piece of wood with 2 wheels attached :

it was my first event with a lot of moments of driving r2 around the 3 very large areas. it didn't take too long before i've got the 2 wheels into the center blocked together on Saturday's morning. the threaded rods was too small and the bolts were not blocked, so every thing was moving. I've taken off my system and simon help me with red loctite. I've repaired my center foot system for the event but i need to change this system for the future