Thanks destruk!
Following the docs and using the "nextpanel" field I have the flashing greatly reduced, but it's still apparent, when nodes are first added to the panelset. Wonder if I'm doing it wrong or if there's a trick to it, or this is just an unavoidable side effect of OverHangPanelSetScene, or maybe of every component if it's caused by what you're saying "
the first time a drawn screen is populated the screen flashes"
aspiring