It will require admin access so I can’t enable it.
But there is a siteconfig parameter which you could add to feed URL so you could try it. You’ll need to URL-encode it. Simplest way is perhaps to open your browser development console and enter:
"http://ftr.bazqux.com/makefulltextfeed.php?siteconfig=" + encodeURIComponent(`
paste
your
site config
here
`) + "&url=<your_source_feed>"
and then open a resulting link to check the text extraction results.
After you get working config you could submit it in a pull request to https://github.com/fivefilters/ftr-site-config so your config will become available on all FTR instances in the world soon after Five Filters will merge your PR.