Aluminum Bar Minirobot help!

[EROCK]

So last night I sketched a design for a minibot which involved custom wheels. I was thinking of simply getting them machined out of 4" aluminum bar . I then read an FTC parts list which stated that we could only use 1" aluminum bar. Is this true? there is no mention of it in the FRC rules about the minibot but I am still unsure.


Here is a link to the pdf packet

http://www.weatherlyrobotics.org/......_9-15-2010.pdf