I think you need a bell crank. Try SWB, but other people have them too. I wish he had pic's of them on his site. I found a pic on his site that shows a 3 servo system that shows the bell crank. It's the bigger of the 4 arms. Hope this helps. Also why is there so much tension on the cables that it does this? Is it at center or at the ends? All over?

http://www.swbmfg.com/

Here's another from Airwild hobbies.

http://www.airwildhobbies.com/MoreIn...&level=2&id=24

http://www.airwildhobbies.com/MoreIn...&level=2&id=32