The heli should loose altitude from that height, and not hover very long. How much pitch do you have at bottom stick and top? In an auto from that height, you are loosing head speed the entire time. 5-6 second of hang time is pretty good though.

I'd run -5 and as much positive as you can get out of it. Once you get above 5 feet high or so you need to be moving forward otherwise you can stall out your blades because you are blowing all of the air out from under the heli. Plus when you are moving forward your blades are more efficient. Then, when you flare, you are still at a little negative pitch, and your rotor speeds up even more. You should flare abotu 5 feet up, and let it settle in.