Good flying mate, My 450 is super stable too, I can do a tail slide from 100 feet and pull out 10 feet from the ground and nothing goes wrong. When I do the same with the 500 the tail gives out and it piros, it is very hard to save it . I have a video I will decode and put up for you to see the problem. I have checked the servo gears and tried a higher head speed and still the same. The belt is nice and tight.

go figure, just a problem heli.
If I can't fix it I will sell it and get a 600 or 700 nitro.