OK I tried the suggested method, but that did not work. So now I have set up the directories in the wordpress pluggin, by click setup to let it do it automatically for me.
The resulting URL to thumbnails looks like this
and path to thumbnails like this /home/shopsia/public_html/components/com_wordpress/wp/wp-content/uploads/store/products/thumbnails
But the after setting up the directories nothing shows at all as you can see here. http://shopsio.com/home/root/datafeedr/
Not sure if thats because I still have the changes mentiond above implemented.