My replacement AP Servo Shear Screw arrived this week ( thanks Dynon ), I fitted the screw IAW Dynons' instructions, all good.
This morning I flew my aircraft and the good news is that my altitude hunting issue has gone away, the AP work flawlessly, problem solved.
For those that maybe chasing an AP Altitude Hunting issue, here's a heads up. Those in the know were pointing me towards "linkage slop" as the reason why my AP was misbehaving, to a point this was advice was correct, however what should be included in the "things to check" category is the Servo Shear Screw.....
Anyway all's well that ends well.
