get the plane up high and nose it down in a vertical downline, or nosedive as the kids will call it. see what way it moves, then you the same thing going upwards. then face into the wind, roll inverted, and put it in a 45 degree anglew with the nose up. see if the nose falls or the tail falls.

this will check for balance and thrust and is worth a try. i think witht he showtime it needs two washers on top left corner and 1 on bottom left. ( that is looking at it from behind the firewall not in front of it.