Howdy Rocketman,
To answer your question. You are absolutely correct about the throttle creeping. It is now only happening below 50% of stick travel. Since I am not using less than this for normal flying it is not a problem. I can work around the lower setting since I am usually setting up for a landing approach.

It was Ron who suggested using the stronger servo. Some info on my setup first. In a previous post I mentioned that I had fitted much stronger springs behind the barrels of both my carbs. The extra load on the servo to overcome the drag was causing a severe dead band effect. This dead band was affecting the way the twin sync controlled the throttles. As it turns out - the stronger servos have helped to overcome this problem.

Kiwi Bandit.