RE: Rudder to elevator MIX should always be used?
My experience is similar to 3D ONdaEdge, start with 10% down rudder to elevator, then adjust from there. Also rudder to aileron, start with 5% and adjust for flat turns with medium rudder. These are pretty much standard mixes for every plane I've done over the past few years.
If I'm building, I angle the firewall for 2-1/2˚ right thrust. If it's an ARF with firewall not angled, I mix throttle to rudder, usually from about 2/3 throttle on up. I have done throttle to elevator on occasion, whether for vertical thrust offset or straight downlines.