You're not tail heavy. I've flown a lot of those Coroplast planes. The flat bottom, high lift airfoil climbs like mad under full power. I finally put some quarter inch under the trailing edge to prop it up and run the incidence down. That helped a lot. Put a piece of 1/4x1/2 under the TE before you rubber band the wing on and give it a try. I finally glued mine on.