Adding rear air outlets?

[dj92]

Hi,
I've been thinking about adding air outlets under the front seats for the back seat passengers :)
That wouldn't be a big thing, an old vacuum cleaner pipe is hanging around somewhere here...
...granted there is a blind plate at the end of the heating box where in cold area spec cars these pipes are attached.
I've seen something like that in a manual some time ago.
Can someone confirm/refute that?