As for the CG problem:

I have the original quest with both the elevator AND rudder servos mounted in the tail since I don't really like pull-pull. Up front I have a Magnum .91 2C with stock muffler (around 25 oz). The tank is a few inches in front of the CG which is rear of the stock location. My battery is a small 720mah pack mounted with the receiver at about the CG. I don't know what the CG is (maybe 175mm from memory) but I had to add ZERO lead. Flys inverted with a touch of down elevator.

Unless the new Quest has a much shorter nose, 15oz of lead and the battery up front sounds wrong. Are you sure you are measuring the CG correct, maybe converting from mm to inches wrong??? Something doesn't sound right.

My Quest, which should be heavier then the new Quest, weighs in the mid 8 lb range (I forget the exact number). Unlimited vertical with the .91 2C stock muffler, 15% fuel, and a 15x6 APC.