> I put some messaging in that code, and it is indeed that bit that does
 > the resizing.
 >
 > Here's a reproducer from emacs -Q:
 >
 > (progn
 >    (setq display-buffer-alist '((".*" display-buffer-use-least-recent-window)))
 >    (pop-to-buffer "file1")
 >    (pop-to-buffer "file2")
 >    (split-window-below)
 >    (pop-to-buffer "file3"))
 >
 > I end up with the following, and file3 in an oddly large window.

So you have been splicing in a 'split-window-below' between those calls.
Why didn't you tell me before?  'split-window-below' copies the
'quit-restore' parameter to the new window and that's what you get.

Let's try to clean up the height value when copying the 'quit-restore'
parameter as attached.

martin