I have the CG on mine right at the very back of the recommended range and it was still very stable, can you move anything closer to the front of the plane? Try placing your battery pack under the tank. I have a Saito72 on mine also, with a APC 14x4w and Byron 15% fuel and it will pull out of a hover, but it really works to pull itself out. As far as RPM's go, try to keep them around 9800 RPM, generally you dont want to go over 10,000 RPM, although I've heard of people doing so without problems.

I suggest moving the RX and Battery as far forward as you can to get rid of the dead weight and balance it in the recommended range for now. Also, you could try fuel with a higher nitro content (if your not already). Good luck, its a fun plane [8D]