Tri-motor ESC and rudder mixer

One of my more enjoyable projects was building from scratch a Junkers 52/3 Tri-motor to drop parachutists or sweets/candies for children at shows. Even though it had an 8 1/2 foot wingspan it was still greatly overpowered by its 3 O.S. 0.25 cu 2 strokes, which resulted in them typically running rich at 1/3 throttle, which in turn meant that I rarely landed with all 3 still running - not ideal at a show. Eventually, I had had enough and am building a sister aircraft to be powered by electric motors. This project is in 2-phases and controls the individual ESCs for each brushless motor. This is phase one which when activated reduces the rpm of the inboard when rudder is fed in. The central motor rpm is at all times half of the difference between the 2 outboard motor rpms. This is primarily for taxiing with a castor tail wheel. The amount of rpm reduction is determined by the trim pot. It also has an adjustable 'minimum rpm' point that prevents the inboard motor from stopping altogether when maximum rudder unless the throttle is reduced to zero. This is to avoid detracting from the scale like appearance by an engine stopping unexpectedly whilst taxiing. Phase 2 is to permit an outboard engine to be stopped in flight, whilst activating a smoke canister to simulate an engine being destroyed. (The beauty of electric being of course that you can subsequently "change your mind" and start it again at the flick of a switch!)