prop selection also helps in backing down in a hover. On my morris knifes. I had one that hovered and backed down great with an 11x4, and a 11.5x4. But on my new knife, (same size and brand engine) It would hover , but I could't get it to back down. So I tried and 12x4APC and everthing is perfect.

You can also hold the plane more vertical, and feed it right aileron while backing down. Holding right aileron while backing down while vertical will help the plane from torgue rolling.