Going back to your question about the old servos. I used to have a philosophy--my cheapest, weakest, oldest servos got put on throttle. I never could figure out why my engines would die in the air when I pulled the throttle back to idle real quickly. It didn't happen all the time, but sometimes I was getting dead sticks when I shouldn't be (plenty of fuel, engine tuned, attitude upright, etc). Even when I would pull the throttle back to idel to just "sail" around for a while, it would idle and then die for no apparent reason, but not always. I also would notice myself constantly changing the throttle trim a click or two here and there. Sometimes up, sometimes down. I finally summised that the old or cheap servos weren't holding their position very well. When you throttle back to idle (say on the final leg of a landing), there is a fine line between the engine idling, and the carb barrel shutting completely, and the engine dying. So I started putting good servos (sometimes digital) on the throttle and I find the idle much more consistent and solid. Not to say that my engines never die in the air, because they do. But this has helped tramendously. Take it for what it's worth.