Hi, out there!
The COCKPIT SX 12 offers all you need with respect to gas and gas trim. Chose "gas trim off" when applying an electro-drive-system. For gas engines use "gas trim on" and don't use "idle in middle", then trim is at one end of the stickway (you can choose which in the controls-setting-menue). Choose "idle in middle" for spezial purposes - I haven't had any of these so far.
One option is missing: gas trim works in all stick positions. Other MULTIPELEX TXs allow trimming just up to the middleposition of the stick.
You can visualize the trim action in the diagram shown in the controls-setting-menue.