Posibility to set width-height of video at render time

[TonKazanKezan]

Somehow Live gets the properties of the previewwindow to set the width and height for the exporting video at render time.
It's not that easy to set the preview-window at a strict width and height, or lock that window.
Two simple textboxes at the render panel would help so the user can set the width and height of the exported video.