Hi phmaximus,
Thanks for all the information.
The motor wattage and amperage are the unknowns to me. In the manual it has motor specifications as:
21 volts power
11 ohms resistance
2 amp empty load current
I've emailed DHK asking for the wattage of the motor.
So basically the ESC and Motor will have amperage ratings. The ESC will need to be higher, but not by too much, amperage than the motor to support it's draw. The C of the battery doesn't matter. That's just how much current it can supply and the mah is for how long it can supply that.
In your video I've seen that small in-line device which does the measurements. I wouldn't mind one of those to check. This is the hobby I want to get into so I'd like to build up a tool kit.
Cheers
Jingo