To those who are experiencing coupling I have to say the reason for this is simply because you have gone beyond recommended specs. I set my cg back  to 5- 5 1/4 and coupling is non-existent during knife-edge flight. Hovers are decent and landings are 3 point. Flies at a tail high attitude with no drop off in inverted flight. I'm using the normal setup with equipment just behind the cg with an O.S. 91FS.