Well, that was eventful! I took off and decided to double check the problem before making any changes, just to be sure I'm not too crazy.
While I did not get the sound again in a roll, it did occur in a straight dive, and in a climbing turn. So I went to check my crash detection settings, at which point I notice I have "detect airframe damage from stress" checked, which I recall is a no-no in Accu-sim. Must've left it checked when I reinstalled a few months back. Anyhow after unchecking that box, I can no longer replicate the problem, so as of now I hope and believe it is solved.
But my problems continue... Being in a hurry to get airborne to do the tests, Genius here forgot to check how much gas was in the tank. So my engine starts running foul and quits before I can make it home. I'm out over the ocean, but there are some great fields just near the shore within easy reach. I'm a little high, so I do one 360 degree turn to lose some altitude... big mistake. That big old 2 blade fixed pitch monster was my personal speedbrake, and I splashed down about 50 feet off the beach. Luckily the salvage and restoration crews are good and I should be flying again tomorrow. Another lesson relearned!
BTW, I noticed I was getting a contrail above 7,000 feet... disappeared below, reappeared above. Radiator temps never exceeded 100. All in the MkIa. Maybe I need sleep, I'll check that again tomorrow.
Thanks yet again, Darryl!