Well, maybe it's the Monokote fumes or all the fun that I had in the past but my memory is just fried. I looked at both my Sukhoi and my Yak and both have Y-harnesses on the ailerons. I would have sworn that at least one used separate channels. They do use two elevator servos on separate channels though which is sorta similar.

First thing I do is go in the flap menu and make the flap switch inactive. Then I mix 100% flap to elevator in both directions. Reverse the flap channel if necessary and that's it.

Is it the right way? Probably not but it works and both planes manage to fly OK.

I'm currently putting together a 27% Extra-330 and I'll be sure to do the ailerons on separate channels. I'll post how that goes.