How does it work set up like that? .. Does the weight of the ball have any adverse effects on the motor. I need to switch my set up to use a belt and pulley system like the real spinners. The polisher doesn't like the weight from the ball and the weight from the pressure while sanding.. the gearing in the head of the polisher gets a little hot and is noisy.. I like your direct drive set up if the motor bearings and bushings can handle it..
I might be able to just use the motor from the polisher in a set up like yours.. I also have a washer that I am getting rid of
I also found that as you put pressure on the ball while sanding and put strain on the motor I think the variable speed resistor in my polisher heats up and therefore changes the amount of volts it lets go... so when you let up on the ball the speed wants to take off.. any trouble like that with your wall mount variable light switch

where did you get your bowl..??