Crossing is not such a sin, I did that way in my SD. Has a lot to do with geometry of the setup. Here's a link to some good information on setting up a pull-pull system.
http://www.swbmfg.com/rudex.html
I started my rudder servo in the tail end of the plane (underneath the fuse) thinking I had a heavy engine (ZDZ40), but moved it back to the cabin area. I used nylon coated wire, but to facilate installation I used those 36" antenna wire tubes to help guide the wires from the rear to the forward area. I just left them in place to reduce rubbing against each other and other parts of the plane. Plus, If I take off the servo arm on the servo, the wires won't get lost back in the fuse, requiring some long sticks to fanagle it loose.
Michael