so there is no movement

Im not sure that that is a wise idea, it is best to allow some degree of movement in ur disc even if jst a few mm so that not all the of the shock is taken by the bearings around the edge, so perhaps some shock absorbers?

We had the same idea as urself in extreme 1 with the middleweight however the small wheels that we had around the chassis were to absorb the impact and keep the disc spinning correctly so to speak. After 1 five minute battle, all of the wheels were bent or buckled out of position. True they were only an afterthought and werent very strong but still u might want to a have a slight bit of give somewhere.

Ill find out about the bearings and get back to you, although im not sure when that will be.