I just got 2 of the same exact racquet (Prince Ozone Tour) and one is 325g strung and the other is 321g. Is 4 grams anything to worry about or is that typical? Should I add 4 g's to the lighter one to make them both exactly the same? One other question? When you have 2 of the same racquet, do you just switch back and forth whenever you play or do you just use the same one all the time and just keep the other as a "spare".