RE: Proper prop balancing
You can sand a little from the heavy side - front and back both. don't change the airfoil. usually it doesn't take too much. You can also paint the light prop with some clear paint. My experience is that the bubbles in the line are usually from a leak somewhere not from foaming duew to vibration. There can be a leak inside the tank just behind the stopper where the brass tube transitions to the tube going to the clunk.