Its a DH86. Having built one at 1/6 scale which flew nicely, this one is at 1/4 scale. The outer engines are well out on the wings and it was found with the earlier model that if one side is pulling more than the other at the start of the take-off run, the model will yaw and at low speeds the rudder is ineffective (its not in the propwash). Once speed has built up the rudder gains authority but the model can be off track by then. This bit of progarmming is to try to counter the yaw before it sets in. The new model weighs 88lbs so needs to be kept on a straight line if at all possible.
The programming is now complete but it used 4 mixers to achieve it: throttle to left outer channel, throttle to right outer channel, rudder to left outer channel and rudder to right outer channel, plus a spare channel to switch the mixing on & off.
This was all done in the transmitter but using the servo limiting (maximum) function in the receiver to prevent stalling the throttles servos at full power plus full rudder.
The new model is finished but hasn't flown yet so I can't report on the effectiveness of the mixing.