ORIGINAL: opjose
Save the props for a pusher and buy new props.
As indicated the thrust line is set for a normal tractor prop. You are introducing some mild inefficiencies using a pusher prop on that plane.
What are the inefficiencies? Electric motors can easily be reversed, as the OP noted, to allow for either a clockwise or counterclockwise prop. I doubt the OP meant counter-rotating, but rather "reversed pitch" or "pusher" for conventional motor direction. The only inefficiency would be running a prop in the correct rotation, but installed backwards - it still produces thrust in the correct direction - but inefficiently. In other words, running a prop in the wrong rotation direction would push the plane in the wrong direction, whether the prop was on correctly, or on backwards.
It sounds like the prop was simply not a good diameter/pitch for the motor.
Kurt