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Herb;
First let me say I don't think your "Dangerously Modified Aircraft" has anything to do with this, it seems far too common a problem. You will have to wait to find a Herb unique problem to blame on your lovely looking mods.
My mechanic believes the root cause of this is both in the elevator trim tab play and in the elevator bell-crank play. Both have a series of hardware (bushings, bolts etc) that are relatively cheap and easy to replace and he claims keep these fresh and you shouldn't have any problems. In my case the trim tab hardware was all replaced by the prior owner and my mechanic replaced all the elevator bell-crank stuff a couple of annuals ago. Again back to his theory, he claims that the elevator is subjected to an inordinate amount of "prop pulse" given how close the rear prop is to the elevator. As I recall it, the hardware in the bell crank was indeed all pretty cheap except for one long bushing. I also recall that the tolerance for play in the bell crank was really tight...their was a series of thin washers that you buy from Cessna as well and then install as few or as many as necessary to get within spec on the bellcrank play. The expensive bushing could have been fabricated I guess but I ended up shelling out to Cessna for it...like $170 as I recall for the one key long bushing.
Hope that helps.
Bill
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