Chuck,

Flat turns typically require a combination of up elevator and aileron opposite to the rudder to compensate for the tremendous drag increase the deflected rudder causes. The amount of elevator varies according to the amount of rudder used. As the rudder deflection increases drag the roll coupling effect generally increases much more than you would think it should. The Sukhoi has a very powerful rudder so small increases in deflection have a very large effect on drag and roll. In essence, you can reach a point where it can require full elevator deflection to compensate for the rudder induced drag. A highly deflected rudder acts just like the brakes on a car in that situation and it takes a combination of several functions to over come the brake. Throttle, elevator, and aileron in this case. When you approach that point the plane becomes extremely sensitive to any changes in attitude and airspeed since the plane is riding the edge of a cross control stall and snap condition. So basically you can only use so much rudder before a mix will no longer have enough offset to compensate. You have to hand fly some things.

The small amount of down elevator required for inverted flight sounds like you're c/g is close to where it should be. If you have one of the planes that has the two position main wing I'm curious if it's forward or aft positioned. If it's aft I would expect more tuck to the gear in KE, but that tuck is normal to one degree or another in many planes. An elevator to rudder mix of about 8 to 10% usually is plenty to take care of this.

Something that's kind of important is that few mixes handle 100% of a condition 100% of the time. Mixes typically reduce the amount of work the flyer has to do, not eliminte that work. You still have to input corrections for different things even with a mix programmed to offset the majority of a given condition. Hope that didn't sound too strange. Basically the plane can't always fly itself once positioned. It needs your input all the time to do it right.