Sounds like Matt nailed it. My Madamoiselle runs on two cells with the C gear (5.86:1) and a 1047 prop. Performance is really good, although top speed is in the 6mph range. Here is the motor/gearbox: http://www.aeromicro.com/Catalog/gws...cs__803650.htm it goes for $17.45. If you don't change the gear ratio, then you need either a motor with a hotter wind (like the GWS EDF50 motor), which would give you more rps/volt, another battery cell-which would give you more rpm, or a prop with more pitch (I would guess a 1080, 1180 or 1260). I belive the A gearing is what Pat Tritle recommended in the instructions.