fixie/single speed electric bike build

Hi ExtraSilver. I'm think of doing your exact build on my single speed bike in London.

Couple of questions:
-What gearing ratio do you recommend? On my bike setup i currently have 47t/17t which I think might be too high a gear for the TSDZ2 motor. I understand it comes with the stock 42t crank but I think this is going to be too low for my desired top-end. What gearing ratio has worked best for you?
-I'm thinking of installing a throttle at a later date to make thing even easier but I'm worried about the motor struggling from a start if using a throttle.

Any experience on this set up would be really appreciated.

Thanks