you can definatly overspeed a 50 SXH with over 12* top end pitch, blade design/weight has everything in the world to do with it here. the posted setup has 9* travel between low and mid stick and only 4* from mid stick to top end and flattening that out some would definatly help with the problem.
And when setting up the helicopter; do you guys get the pitch curve right and then tune your engines to get the RPM right, or the opposite? What about the throttle endpoints? Whats first?
first thing when starting all new is to set the radio so you get equal travel from low to mid and then from mid to high sticks on BOTH throttle and collective. then divide your total collective travel by 2 and that is what you should have at mid stick. i don't know what the hang up is with some folks that you have to hover at mid stick, all mine hover very slightly above mid (slightly below for inverted) and anyone who has progressed past learning to hover and plans to do any sort of aerobatics/3D/inverted should then learn to fly with 0* at mid stick. then adjust your throt curves for the desired rotor RPM you want in any particular flight mode.
I've been away from this board for the past 5 yrs (it was rc online when i left) and i can't help but notice that allot of posts incline that less experienced people should use different pitch curves for different flight modes, this is one thing I've never agreed with and never do. i fly max collective travel with the same pitch curves in every flight mode, that way the heli's response is always the same to stick input and regardless of the situation that arises i don't have to worry about flipping a switch to have the correct pitch curve to save the day.
kc