control zoom in playlist's XML - how?

[nomnomnom]

I registered just to ask this as I cannot Google up anything sensible... What I want to achieve is putting XML tags in the playlist file to set the video-zooming to 50% as I have a set of files that are wider than my screen.

VLC can create a playlist which is in XML format. In that documentation is mentioned control of additional parameters using [vlc:option]option-name=value[/vlc:option]

In the command-line documentation, zoom gets a superficial mention "--zoom=float". No detail exists if this float is in the range 0.0 to 1.0, or 0.0 to 100.0 or anything.

I have tried this, with no success (avoiding &gt and &lt as forms munch them):
[track]
[location]first-video.avi[/location]
[duration]146000[/duration]
[extension application="http://www.videolan.org/vlc/playlist/0"]
[vlc:id]0[/vlc:id]
[vlc:option]zoom=50.0[/vlc:option]
[/extension]
[/track]

and varieties like "video-zoom=50.0", "zoom=0.5", etc. Nothing. Is this possible and if so how do I achieve it?
Thanks in advance for any help with this.