Thank you for the analysis.

There are two aspects you can look into.
The first may be to create your own Template. When saving you can untick Show preview.
The second to to see if you can access the Xara .WIX format and export your page to that, deleting the original. When saving, you can exclude the Preview image. For me, a single character A4 file is 2,696B.

You originally mentioned the image file size was 32kB. You now are reporting TAG_PREVIEWBITMAP_JPEG with 6,497B.

At no point can I hit 49kB.

All this tells me is you should not be saving design files with only one page of text.
Offer up a 'page' from your website that we can dissect to see how well we can do.

Storage is cheap and single paging everything is not efficient for search and retrieval.
With a MarkDown system, I am able to render as HTML and directly edit the page contents through that render with none of the Xara 'overheads'.
It comes with a built-in search mechanism and is older than three years.

Acorn