It's worth noting that although the wheel size changing option does work, it does completely void your warranty.Kalkhoffs can have their cut off changed by using the dealer diagnostic device which they will lend you to update software. It’s just a matter of inputing a smaller wheel size. They all cut out at a bit over 17mph anyway and not all bikes use the 10% tolerance in the law. Most seem to cut out bang on 15.5mph. Dongles are also available for it.
The badassbikes dongle is probably the better option whilst in warranty!