After working with some nylon shims I found the correct size for the shims.
It will require a 1 inch and a 1/4 inch Aluminum tube shim along with 3 flat washers.
Now that this is behind me, I will finish up the motor mounts and will start on the
wheels for the center foot.
It will be nice to be able to move R2 around on his wheels, He's getting heavy enough that I have to drag him around.