RSS feed with *all* active threads in a forum?

[Ville]

I'd like to create a RSS feed that would list all active threads from the selected forum(s), not just the recently added threads (that seems to be the default with vB 3.6.7). While this is probably a very simple thing to create, I haven't found yet a way to do it.

If I use, say..

/external.php?type=RSS2&forumids=8&count=15

.. I get just a list of up to 15 threads that were added recently. How to make it show all the threads with recent posts in ascending chrono order (most recent first), limited by the cut-off date, and by the maximum item count?

Thanks for any insights or pointers!