You have to get the plane really stable in knife edge before it will do a KE Loop. You also need a LOT of power, at least 2:1 to really make them symmetrical.
There are SO many things that can help or hurt with coupling issues due to thrust, incidence and cg.
Heres a start to simply mix out what you now have,,,, on a day when there is <5mph wind fly straight into the wind on knife edge with just rudder and see what the plane does. Do NOT correct with the right stick while you are testing for trim, just watch what it does.
1. Rudder to Elevator- Its either going to fly straight, pitch to the belly, or to the canopy. Put in a Rudder to elevator mix that is always on that puts in the appropriate elevator input to counteract the pitch coupling so that the plane flies on a straight line in KE. DO this on both knife edges. Dont make assumptions, check both left and right KE. The mix may be totally different of left and right KE. No switches to activate, leave the mix on all the time. Play with it till you can fly straight into the wind with only the rudder. No elevator or aileron.
2. Rudder to Aileron- Its going to fly straight or its going to roll to the left or right. Put in a rudder to aileron mix that puts opposite aileron to couteract the roll. Set each side seperately and be thorough. Same as the other mix do not put it on a switch, leave it on all the time.

On both mixes you will probably not need more than 10% mix to correct. Work in increments of 2 until you get it close and then tweek it down till you can fly on KE straight into the wind with only the rudder and the plane tracks arrow straight.

Once you get this right it will do better flat turns and anything that involves the rudder. The things the coupling screws up in KE it also screws up the rest of the time, you are just trimming it out.

Once you get this done you will be able to do better KE loops but even with a well trimmed plane you STILL have to correct with elevator and aileron a little as you progress through the loop. The only way to minimize this is with a rudder to elevator mix on a curve and a perfectly balanced plane with the right type of rudder.


Here are some other things to consider on KE that are about the fundamental setup of the plane.

1. Pulls to the wheels, could be noseheavy
2. Pulls to the canopy, could be a little tailheavy
3. Has roll coupling, may need to be laterally balanced. (Add weight to on wingtip or the other to truly balance the plane from tip to tip, this is very important by the way if you want a a plane that flies true.)