i have seen these scooters in action. i weight 100kg (ish) and having ridden a very good one, i think you are JUST ABOUT able to use them. it will be right on the edge as far as performance goes, you are getting near the bottom end of what i would say is useful power/speed. these would make brilliant featherweight drive, but middleweight... i wouldnt.

but then, if you can double the gear ratio and overvolt them 100%, maybe this is getting reasonable results? i imagine youd get good performance in this situation, but life expectancy would be an unknown.

hope this helps