I have just bought the oxygen s cross I did the code thing , 12 worked for me , the speed seems to top out at about 22mph on the flat, I fitted a throttle and it still achieves the same speed, if you go down hill the speed increases as you would expect,if you lift the back wheel the speed gets to just over 23mph and thats on max power setting ,so I think thats all the motor can put out,anyway when you have spent years doing 15.5mph 21 if great, on another tack do you thing brexit will mean we can ignore the stupid 15.5 anyway and all put throttles back on without plod chasing us down the road.