"Has anybody else noticed the annoying way these overlays flicker when playing a clip?"

Yes.

"Any suggestions?"

The only time I worry about them is when adding text or graphics. Turning them off during normal preview would be my suggestion if they're bugging you. I've yet to see any monitor or TV mask off anything inside the 10% action safe area and I can eyeball that close enough without an overlay. On top of that pretty much once it's shot there's not much you can do about it anyway if it's outside safe area.

Bob.