I have been flying a world Models 120 Ultimate for quite a long time now. This is my second one. Don't ask about the first. The dimensions between the Goldberg and the World planes are within 1/4" of each other

My Ultimate weighs in at 9 1/2 lbs. wet with a Saito 1.50GK. Using a Zinger 16/6 prop and 10% fuel, this plane will hover and torque roll all day and climb out straight up. I have noticed that the guys flying the Goldberg Ultimates always seem to stay in the 70 to 90 range with their 4 strokes. Your engines are too small for 3D. 3D requires POWER!! Step up to a 1.20 size engine on the Goldberg planes and enter a new flight envelope.

Don't worry about the added weight, the engine will pull itself just fine. Your Ultimate will 3D just fine with enough power and control throws. Remember that it's a biplane and has some differences in the stall from a mono wing and encounters a few limitations because of this. It also has a much higher wing loading than a mono wing.

Silversurfer