Yes, but with that radio I'm sure you can slave any two channels. I have the same radio at home. I do not, however, have the setup you are referring to, so I've not tried this, but can you not slave the elevator and gear channels together? Ailerons and AUX1 together?
If not, then slave elevator and AUX1 together, and use a regular Y for the aileronsthe ailerons you just have to put the pushrod on opposite sides of the servo. This will eliminate the need for a reversing Y, which I have always found to be a point of weaknesseither in failing all together, or the POT constantly being messed up, and having to re-center the servos.
Any Mixing you do on this radio for this purpose needs to be on mixes 6 and 7, as those are the ones that provide single lever trim functions from the face of the radio. If you try it on other mixes, you'll quickly find out what I'm talking about.