Jim-- about the Align motor, Align recommends the 13T for a TRex, which has a 150 tooth spur gear. The 12 fewer teeth on the MX spur will make for about 200 RPM higher than the TRex, for what it's worth. At 3500 to 3700 kV (430L or 430XL), I think Tex is right on the money for the gearing.