Nobody has recommneded reading the engine's instructions, why? All of the engine instructions I have for the engines I've bought have a recommened range for propellers. If you go with somewhere in the middle of the range, it will be a safe size to use. Change to other sizes after you've flown and determined how to get more power or speed if that's what you need. Not bad mouthing anyone offering advice here; but, I will guarrentee the manufacturer knows more about their product that anyone else.

I balance every prop I use. APCs and Master Airscrew props are sharp as razer blades when new, I remove the molding flash and sand the edges to give a safe feel to them. I find doing so generally improves the balance. Wood props will in all likelyhood be out of balance and need balancing. I think it is so easy to balance a prop that it simply makes sense to do to everyone. By the way, remove the price tag!