First thing I would do is give it more pitch a 1/2 stick. 4.8 sounds a little low to me. I would try about 5 or 5 1/2. Then you should be able to drop your throttle curve back around 50% at 1/2 stick. The way you have it setup now, It must be screaming at 1/2 stick? Do you have a tack for checking you head speed? If not you should buy/borrow one, it can save you alot of work. Maybe find someone to help you set it up.