I have done many (can't remember exactly how many, but more than a dozen) DONE4's. Never had an op-up on any of them. Once almost had a downgrade at the gate on a BA flight following a last minute aircraft change from NCW to OCW. The OCW had less seats and I was handed a Y boarding pass when the scanner rejected my original BP. Luckily, another passenger failed to make a connection and I got his CW seat. Perhaps I should have taken the Y BP and asked for a palm tree?