ok i just sent mike an email....

i mocked up to check .... and it should work sweet, i used spacers i had and i think its about 4mm thick so that is right, and i will have to dremal a very little on the outside brake pad (1mm) and will also trim a small amount off the heatsink/motor clamp to ensure the brake disk wont hit .. heres some pics from my mockup, oh and i have plenty of shaft for pinion mounting, i used a 15 tooth in mockup but i should be able to use less as well