After installing new engine mounts and reassembling everything we still had a modest vibration of the assembly while under power, increasing with RPM. After loosening the bolts that hold the Vetus coupling together and to the transmission output hub, the bolts were not at all under pressure (shear) that would indicate misalignment. In fact they could be slid fore and aft easily with a finger. The coupling and transmission hub separated about the distance of the thickness of a business card, and the gap was uniform at each of the 4 bolt locations. Seems to me this is about as good as it gets for alignment. Is that precise enough?
Suspecting the remaining vibration is from the Autoprop. Bearings replaced in 2009 with maybe 1000 hours on it since then. Seemed OK 200 hours ago when examined on the hard, clean and no wobble in the bearings. Total hours probably approaching 3500. Does the Autoprop need to be rebalanced from time to time?
