I included a Hill-Climb and Force-Calculation in Version 0.2.
The magic (physics) behind this is the following: We use the ACTON QU4TRO, we don’t know the exact specs but we do know: 36V (10S) 400W Hub-Motor x 4 Wheels 99mm (I know they announced to change the wheeldiameter but for this calculation we use the old specs) TopSpeed 37km/h 7,7 kg
That’s all we need, first let’s guess the motor-kv, it have to be about 55 rpm/V (You can calculate this, but I simply type in different kvs in my tool until the speed matches the marketing specs)
36V x 55 rpm/v = 1980 rpm (motor rpm) This board has no gearing, so the wheel-rpm is the same
We asume we have a power loss of 25% (to heat and shit), so the max power that is transfered to the wheels goes down from 1600W to 1200W
What torque is that: (9549 * kW) / wheel-rpm so: (9549 * 1,2 kW / 1980 rpm) = 5,79 Nm With 99mm, the force that can be put on the road is: 5,79Nm / (0,099m / 2) = 117 N
Final step, we have a 100kg person, what is the max hill he can climb: asin(117N / (100kg + 7,7kg) * 9,81) = 6,35° = 11,14%
The downhill force of a 107,7kg mass on this hill is 117 N. That’s the force the board have to produce to maintain the speed of this mass. If you want to accelerate on this hill, you need more. And there is also friction, but we have already calculated a energy loss of 25%.
You can change all of these parameter to whatever you like and do your own calculations.
ACTON claims a hill climbability for the QU4TRO of 30%. Hm, this is possible if the person is 34kg. 
If we have 100% efficiency, the person can have 48kg, yeah maybe they tested this in china with chinese people…
Otherwise we do need more powerful motors or smaler wheel diameters, or something is wrong with my magic, äh I mean physics 
please prove me wrong if you can 