darticus:

You want about 45% at the elevator, and ailerons, all you can get on the rudder. Go into the control horns on the control surfaces and get closer to the surface, first or second hole from the surface as necessary. You will continue to have this problem on your 3D birds until you order some longer servo arms which will increase your throws as needed. Try to keep reasonable mechanical advantage at the servo and control horns, or the servo will suffer.