PatMike, DJI and others have recommended not flashing the Phantom.
Other questions answered.... to Dewster and Pilotman.... From what I can gather, and I can see it when I test my motors....
When you arm, the motors will start up and idle, will cut out of less than 10% throttle as before. You can move your stick up to 50% and you will have no reaction to prop speed, still at idle until you hit 50%. My 550 due to weight, sits on the ground still which is very lucky as I was testing this in my front room. The idea is to get the motors up to speed and get it in the air, once in the air and I presume a few feet, you will have 100% of your throttle back.
Not sure how it would handle a broken prop, more than likely, a 450 would not handle it at all without flipping, a 550 or any hex might. I have heard these units compensate for a missing prop, but I can't verify that as it has not happened to me.
Still waiting for better weather to test my new load out, can't wait! will report back.