Your post reminded me of a couple of sites I remembered from way back when.
One was called RundeKunst.de. I think it's fully German, but maybe it rings a bell.
https://web.archive.org/web/20131126131712/http://rundekunst.com/index.htmlAnother just had a few stories, some in German and some in English
https://web.archive.org/web/20060907172640/http://mitglied.lycos.de/cybermonk/index.htmlSome of the earlier captures on there have some links that may lead you to some other older German feederism sites.
I found another page with a lot of German site links on it, but didn't look through them all.
https://web.archive.org/web/20020716192925/http://ssbbw.de/links/links.htmlI also would look at the old Feeder UK site on the wayback machine. It had a good number of links to European BBW sites.
https://web.archive.org/web/20060226214620/http://www.feeder.co.uk/Best of luck on your search!