would this fly
It is not the engine it is the plane. The plane is a lead plated brick. Mine with a FSR .25 flew like manure. I had micro servos and as light a Rx battrery as I could get away with. You add the weight of the 4s and you are right, it will not fly at low throttle.
Dru.
P.S. I do not know about the other plane. What is the weight and wing area?