I haven't used air tropics in years but the simplest way is Y harness with a servo reverser.or use a match box.a few bucks more but then how much have got invested in your prize bird.i always avoided twin elevators as it was truly a pain programing.to my suprise when I transitioned to a new futaba 8 radio I had to set up split elevators for my 30 cc edge and when I made a few simple connections and touched a couple button I was so amazed it just workeno zeroing out no mixing.what a great systemd