i will not buy a new motor yet.
it was not possible to change my order so i will try 12/72 or 12/70. wich gearing give me the best acceleration?

you told me "Gear DOWN for faster acceleration - gear UP for faster top speed..."
it that the spur och pinion?
will a smaller pinion help me get better acceleration?

Gear down means smaller pinion or bigger spur

Gear up mean bigger pinion or smaller spur