4QD controllers have long been used in electric go-karts: many years ago there was a commercial indoor go-kart arena where the karts used Lynch motors and 4QD-300-48 controllers. This made a powerful full-size machine. Although it lacked the exciting noise of the petrol kart, this did mean that it could run in a built-up environment without complaints from the neighbours.
Of course our controllers are often known in kiddie kars of all types, many of which count as go-karts.