I'm inclined to go along with Captainjohn,Check to see if you have any elevator mixed in with your throttle.
Are you sure you have 4% of down thrust?.You can just eyeball the profile of your plane and see if you have up or down thrust.
I'm also inclined to think you don't have any.As far as CG goe's if it was that tail heavy,you most likley couldn't fly it anyways.Finger ballance on the spar line should be a good place to start i think.Just my two cents worth.

Dick