Maybe I get it now. I’m not using the Page Header addon (as I said in the first post, I don’t want to let users control the header, I just want to build my header in the theme with a little more flexibility). I kind of thought that the function you provided here to copy and paste would crop images on the fly. If it doesn’t, and it relies on existing versions of images, then what has happened in my test makes every sense.
Thanks a lot!