It might be the back right corner of the baffles hitting the top cowl on shutdown shake. I have a similar spot on my cowl and determined that was the cause. Reach in and check the clearance there,
So glad you are up and flying - it was great to meet you and have your help on the PnP mission years ago!!
Amateur Plane - RV-9A N789PH - 2400+ Hrs
Amateur Radio - KD0CVN
Doggies Delivered - 25+
St. Paul, MN