In the early days of this Katana 140 ARF there were issues with the CG but nothing as extreme as what has been posted in this thread.
I bought two of them back in 2003 and assembled them stock out the box and didn't add any weights to balance them. The three Futaba servos that I used in the tail were lighter than the heavier Hitecs that most people were using. The engines were OS 1.60's with Bisson Pitts mufflers.
If it will help, I'd like to state that my CG was located at 135mm back from the leading edge and both planes were very good aerobatic fliers.. The instruction manual specifies a CG range of 110 to 130mm at a distance of 150mm out from the wing root.