To expand on what David says here. I'm also using Aux 2 for the left aileron. Then go to the wing type screen and mate "Elev" with Aux 2. (Make sure you have the "Aux 2" switch inhibited). When you go to the "DR & EXP" and "REV SW" and "SUB TRIM" screens you will now notice that instead of seeing "AUX 2", it will say "LELE". Pretty neat it think. Also, as David says you don't need to mix anything.

Jim