This is the first chance I have had to get the transmitter in my hands for a long time to try and explain how I set it up. Please bear in mind I sorted this out months ago, after much experimentation and cannot remember exactly how I did it, but here goes.

I assigned channel 3 to (Throttle) left hand engine and channel 9 to (Throttle 2) right hand engine. I then assigned switch SG to control the selection of what the stick controls. To the rear you can start the left hand engine whilst the right remains at tick over, changing it to fully forwards allows you to start the right hand engine whilst the left remains at tick over. The centre position allows control of both engines for flight. The trim for both engines is on trim 3. You also need to set Master and Slave the opposite in the forward and back positions, this enables one engine to remain at tick over whilst you start the other, I believe that this is done by changing the group/ single mode in the menu but cannot check as my battery has just died.

Please note I have not flown this as yet, but it appears to work correctly when observing the servo monitor. Hope this helps.