draw:image vs draw:fill-image & multiple copies

[Dr. David Alan Gilbert]

Hi,
  (Context: PDF importing a weird document with thousands of identical
images https://bugs.documentfoundation.org/show_bug.cgi?id=88914 )

If you insert an image into a Draw document you get a
  draw:frame with a draw:image inside, with the image data

If you duplicate that image (copy/paste), you get a second
draw:frame and second draw:image with the data again.

Is there any way with draw:image not to copy the data?
I wondered if it was doable with a
  draw:image xlink:href=hmmsomething
but couldn't figure out if it was possible to link back to your
own images?

But the other route is a
  draw:custom-shape
   to a style with a draw:fill-image-name
     to a draw:fill-image

and then you can have multiple draw:custom-shape's sharing the
draw:fill-image - and hopefully the style.
Is there any downside to that?

Dave
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