Using the gas-powered Mosquito as a baseline, its manual says the engine is 12 kW:
Those Turnigy RotoMax 150cc motors are listed as 9.8 kW:
https://hobbyking.com/en_us/turnigy-rot ... motor.html
So two of those would be 19.6 kW. Assuming that 9.8 kW is input power and actual output power would be based on some efficiency factor at your operating conditions. So the minimum efficiency to match the Mosquito would be 12/19.6 ≈ 61 % (assuming that the props that you would use on these electric motors also have similar prop efficiency to the one of the Mosquito). Which seems reasonable, although I am far from an electric motor expert.
You'd also have to consider your total weight in batteries versus desired runtime. Current draw would dictate size of the ESCs needed and related wiring (more weight). You'd also need a throttle system compatible with launching and flying a hang glider (bite throttle like Mosquito?). My quess is that the runtime/weight of the batteries is going to pale in comparison to the runtime/weight of gasoline.