I wouldn't hesitate to run 48V / 30 amps on a MAC
I agree with dogman, this is the data that has been accumulated by dozens of posters. The true max depends on the application. If you are on flat land, then the motor will draw max amps for a couple of seconds, and as soon as you attain top cruise speed, the amps drop down and simply maintain speed. You could probably go to 1500W often if you give the internal parts time to cool off between accelerations.
If you do all of the bad things, you must lower the max amps.
A. Tall wheel like a 29'r
B. Use max amps on a long uphill
C. heavy rider + cargo
D. A, B, C at the same time.
I recommend a 24-inch wheel, and a 2.4-inch tire to make the tire the same outer diameter as a common 26-inch (if mounting the hubwheel on a 26 frame). Doing this may require a frame with a rear disc brake.
MAC is a geared hubmotor, and it has a poor heat-shedding path. Ferro-Fluid does not help geared motors shed heat, only DD hubs. For a geared motor, you have the option of adding a coffee-cups volume of ATF, or drilling ventilation holes in the sideplates (which causes its own problems).
The plastic gears act as a mechanical fuse. If you get the motor hot, the max torque before damaging the gear-teeth goes down, so....max performance is attained when the gears are cold at the beginning of a ride. If you want to use more than 48V X 30A = 1500W on mild hills (or flatter terrain), then buy a spare set of gears when you buy the MAC. Your hills/body-weight/wheel-diameter are not like mine, so my max power on a MAC is not the same as your max power. Get an internal temp sensor, so when you fry the gears, you will know what your true max power is.