That's certainly better. I seem to recall running into some other app that had similar problems with a maximized window on the Mac, but the details escape me.

Sadly, it doesn't remember where I put the panel split for the next session - the default is a little too small, particularly for adjusting the theme image crop focus, though It's easy enough to "bust out" of that one, and get a large version to tweak.

Now I can die happy.