FAA published the final rule, AD goes into affect Sept 15th. Looks like I may have narrowly escaped the date range for the cylinders in question, know at least two others who didn't. Make sure you 520 and 550 owners know how to comply.

https://www.aopa.org/news-and-media/...ide-opposition

https://www.federalregister.gov/arti...g-engines#h-64