I love Calibre's ebook-viewer.exe, but I also love old software

and sometimes use a DOS file-management shell [ProFinder, which came bundled with WordStar for DOS] that can only pass on short filenames (8.3-style) to other programs, such that an ebook file with this name:
Quantum Night - Robert J. Sawyer.epub
has its named passed on to the Calibre ebook viewer as:
QUANTU~1.EPU
The problem, of course, is the extension .EPU, because the Calibre ebook-viewer.exe doesn't recognize it, and so gives this error message:
ERROR: Could not open ebook
ValueError: No plugin to handle input format: epu
Would it be possible to add the ability for the ebook viewer to recognize .epu as a valid synonym for the extension .epub?
Thank you so, so much!