Keith,
I've had an MX-22 for over a year and still don't know all the tricks. If you want to use your trim as a kill switch you can either assign a switch or bump the trim rate to course setting (10). I'm not a fan of electronic trims on throttle either.

As for the gear setting. Think of the flight mode as if it a new plane. Once you copy the first mode into the second, you can change anything from soup to nuts into the following modes and not affect the prior mode. If you want the gear to come down in land mode, just reverse the servo in land mode. I'm sure there is a more elegant way, but you just have to play around with the radio and see what the controls do. If you mess something up, just copy the origional settings into the mode you're workin with.

Hope this helps.

Mike