First and foremost WELCOME to RCU !!!!
JUST to make sure we're all on the right page here... the Hawksky .. basically the same airplane as a Bixler... styrofoam airframe, brushless electric powered with a pusher motor configuration...
there are a couple of thing to be aware of... (I've got two bixlers and love them! very easy to throw in the car and fairly aerobatic when set up properly.)
you've mentioned that the prop is pushing air (as it should) .. but is the front of the prop still facing forward? (it should!) the front of the prop is the front of the prop, does NOT matter if the motor is mounted in a traditional tractor setup, or in a pusher configuration. the front of the prop should ALWAYS face the front of the airplane.

upthrust: again, since this is a pusher, in order to get more 'Upthrust' (advancing the throttle tends to push the NOSE of the airplane upwards) you would need to add washers to the TOP two motor mounting holes.
(that airframe has a considerable amount of DOWNthrust built in... double check that your 'upthrust' is not in fact DOWNthrust. )

additionally, since the motor is mounted way up higher than the aircraft centerline, adding throttle will momentarily cause the airplane to pitch DOWN.

one last thing.. my bixlers require a fair amount of up elevator on takeoff... once it's airborne that requirement goes away pretty quickly.