Torrent adder doesn't work properly with private trackers.
So i found an alternative (works on Chrome & Firefox).
An extension called "Xirvik .torrent to seedbox uploader" (chrome version, firefox version).
You can't configure it like Torrent adder (No port specification/ssl etc) but it works fine for me
Let's look the configuration :
Note : the Seedbox URL can be like "http://IP_adress/rutorrent" also
How to use it :
When you visit a torrent page, just clic on the habitual button for download the torrent. Some seconds later, you'll see a notification that tells the torrent has been added to your seedbox.