on highendrc web sight it says 4.75 x 4.75 but if you have a watt meter i would try 5.5 x4.5
i had the 2w and put 600 and 800 watts to it and it held up and it's only rated for 450watt so if you go over the 750 yours is rated for no big deal as long as the motor is not get hot
hope your batt can handle it
whats your c rating i hope 35c or 45c
i just ordered the 1w-30 today 1400watt motor
try this on 4cell before i go making it a 7 or 8cell set up with 2500 watt or so
i want to see how the carbon fiber funjet handles the add weight of a 4 cell 5000 45c batt before i go putting two of them in there