Great, I hadn't even seen that the .ora format produces a stack.xml file that contains all the layer names. I'll be able to script and give the correct names to the 140 image files!
Yeah, I'll cut a few, but I'll stay above 130. Luckily the renaming script works, and I can import the images into Advanturon with a .zip file.
I don't understand why .png compression with Gimp is so bad; https://compresspng.com/ seems to be the most efficient, but it only takes twenty images at a time.