Everyone always says, "A lighter plane flies better", but really, unless it's a 3D plane, don't lose any sleep over adding a few ounces. Move the battery if possible, but then add weight if it needs it.

I DO like to make sure that any added weight is going to stay in place. Stick-on weights may be ok on the tail, but they will eventually come loose in the engine compartment due to the oil, so I use screws or epoxy.

It's also a really bad idea to add weight to the cowl ot tail wheel bracket as they were not meant to carry such weight, so the vibrations could cause a cowl to crack or elongate its mounting holes - likewise the extra weight on a tail wheel bracket could cause the wire to break (even if it has a spring)

BTW, regarding my first statement; I have had two planes which have required over a pound of nose weight and one that needed 11oz - they all flew GREAT!

Also, I prefer NOT to add weight to the crankshaft in the form of heavy washers or a weighted hub. In the rare event of throwing a prop in flight, you now have to land a tail heavy plane with no power!