Originally posted by Sportive
I use 13x4 apc in my flip 3d(irvine 53) hover at half trottle!! When i use 11/7 or 12x6 my flip hover at 3/4 -full trottle....
My advise try 13x4 !! 
Yup, that's what I'm using...APC 13X4 W
Perfect match!
It ain't the speed you need...