I had a couple of questions about props, currently flying with the stock ones. Is the any reason I should upgrade? If so to what, and how can I make sure they are compatible? I've read that certain props aren't balanced (whatever that means) or certain ones only work with certain models? What is the difference other then length between 8" and 9" props? Ebay is full of props, but I've read some horror stories of props flying off mid flight. My primary use for my copter is filming with a gopro attached if that matters. ~Thanks in advanced!