Several questions

[suicideneil]

I believe the HV4.5 is rated at 4800kv (6.5 is 3100), and size wise its just a few mm shorter than an XL can motor. The catch is that the rotor/magnet is only 380 motor diameter, which is why it struggles to propel larger/heavier truck around. I have the 6.5 in my Gmaxx and it is only reaching 30mph or so, which means the 4.5 would be faster, but a lot hotter and may fry. You can find the kv ratings of all the feigao motors in BrianG's speed calculator, which is in his sig.