You're right. Thanks.
But I hadn't tried SUPER72 modes in interlace before, and the Indivision seems to deinterlace them incorrectly. Are they working for everyone else? Mine look as if the fields are rendered in the wrong order. It's making graphics garbled and text hard to read. For instance the almost blank line underneath the crowded baseline of text ends up on its upper side, and similar throughout.
I also got another copy of the top of the screen in the bottom at times.