@imalcolm @mnemonicoverload Moppet was the same. I kept her to just two rooms, and after a year of that I realised I'd forgotten for weeks to put up the barrier to the rest of the house. In all of the two years I had with her, she never once strayed past that doorway.
What's the diameter of the ducting that's been working for you? I believe I need a trip to bunnings.