4mm only? Those tooth will be stripped during the first decent acceleration.

Just to give an example of forces on gears. Kashei, a feather stripped and split steel mod 2 gears , and the motor dirving those is just a NTM5060 on 4S. We had to redesign the geartrain 4 times, to get something that doesn't eat gears every fight.

I was thinking of mod 4 ringgear for the disk, and those are 40mm wide in commercial form. Idealy, it would be chevron gears.