Actually, I’ve found a property called android:zAdjustment in the animation files.
If I put android:zAdjustment="bottom" in hold.xml (screen 2) and android:zAdjustment="top" in push_down_out.xml (screen 1) then I can get the desired effect.
This gets around the z order issue (I assumed it was an issue with animation timings so I was barking up the wrong tree).
John