Ok thanks, i have come up with a new, very siple way.
I dont know how i could have missed it, and theres no need for a removable flag, it is solidly in, with a removable link at the top.
Instead of the axle down the centre of the bearing spinning, the outer casing for the bearings spin, and so there is able to have a longe, solid axle straight through the centre of the robot with no problems (hopefully anyway)
Will this be ok?
Grant