Here's a hack I found for sizing screenshots. Not ideal, but it works:
- Create a custom paper size that works with your OO document. (I found 6" x 4" worked for my purposes.)
- Print your large image as a PDF in the new custom size. Keep your margins as small as possible. The PDF document will be high resolution but constrained to that paper size.
- Import into OmniOutliner. OO respects the PDF size, so this works well.
Incidentally, it also helps ensure uniformity among your images.
Regards,
Dan Byler