Hi Stokes, Ihate to be the bearer of badish news, but the kb 45 8xl doesnt spin that fast on 4S, I am running a single one in a 35 inch cat, so far have only gone about 42mph or so, with an M447, I spent the night polishing a x450 to try today, so will see how it goes. you will have to run MONSTER props to get any decent speed on 4s, The do have insane torque though and make my cat wheelstand if i punch it out of the hole!