I'm glad to hear that this is working for you! It gives me hope.
Bernie has started doing this with Kirby (my poor ancient mix), and even though Kirby outweighs Bernie by a good 20 lbs, he can be taken down in a second (he's so wobbly and unstable). I've started making Bernie sit or holding him and letting Kirby out first.
Do you think it's wrong to hold him instead of commanding him to sit? (Usually when the door's opening, I've got Ginger, Kirby, Bernie and Fun Kitty all trying desperately to get out. Since we're trying to keep Fun Kitty in, it can be a real zoo.