Although you have already labored the point fairly well I thought I might just add my 2c worth about balance.

Obviously the best way to balance the aircraft is by moving components which are already onboard - clearly the battery is the biggest contributer here, but in a smaller model even where you put the reciever can matter.

However, if that doesn't do it then you have to add whatever weight it takes to make the plane balance. Of course you want to keep the aircraft light, but if it is not correctly balanced, particularly as a beginner, you are going to have a very difficult to control and not fun to fly aircraft. To add as little weight as possible make sure you add the weight as far forward or back as possible (in the correct direction). However, avoiding the idea of packing the spinner with clay or anything like that. Chances are the clay wont be evenly distributed and you will unbalance the propeller introducing vibration.