Back to that picture and A 1000 words thing. This is A really old scratch built plane I did about 10 or more years ago. There are A lot of ways to end up doing the same thing but this is the only plane I had handy with this old system in it. I have also made up Ys by soldering and bending 4-40 rod to custom fit A plane.
In this case I used A carbon Fiber arrow shaft, I used to have them in all sizes because I lived in the country and deer hunting came early for archers. During practice they tend to robin hood arrows and destroy them so I had my friends save them for me. The tip I used on this one you can buy, they even have kits to do this but free is better.
When using A Y I don't use the wire between the two elevator halfs. The Y can be used to trim each side as needed just like using two elevator servos and/or adjust for any warp.
Remember too that elevator rolling can be caused by too much elevator throw too, well, that and A few other things but this is A Y system.