I agree with Fizz. You're trying to justify this out like a math problem. -4 degrees plus .3 degrees plus zero degrees does not equal a good flying plane. All of these angles will create forces that will interact differently over the range of speed the plane goes through.

I also agree with Gary. You need to get the fuse, motor mount and tail to zero, zero, zero, then trim the wing to get it fly straight. The plane will need ~4pounds of lift to fly straight and level. Teh wing needs some angle of attack to make that lift.