First and foremost....unless it is a HOT .15 motor, I would say that I would want a little more "umh" for my motor. The Speedy Bee is heavier than the Lazy Bee and it is a very draggy plane to begin with. But, it should not want to dive like it is doing.

#1 So....If the CG is on the money, I would be looking at the trim of the elevator.

#2 I have a good 2 inches of travel each way on the elevator.....you need a lot of travel to compensate for the turbulence coming off the flat bottom wing and the elevator is VERY close to the trailing edge of the main wing. You may not have enough!

#3 ....I would check to see if the bottom of the ailerons ailerons are level to the bottom of the main wing. If they are hanging down below the wing bottom surface....they are in effect becoming flaperons and you will need much more elevator trim an input.

#4 I would check to see if there is excessive down thrust on your engine.

Hope this helps.....please let me know what you find!!!!

Dave