tchirou
Hi,
Thank you for all your useful suggestions, but we are not going to do this one.
The mail hall serves the purpose of entrance, it is not the same as the void scene.
For example, the Oculus main dock won't let you change the vertical position either.
If you want to control the content while lying down, I think you can play the video in Void/SpaceStation/Moon, drag the movie on top, and lay down to watch it, and later you can open the file browser on the playback menu so you don't have to enter the main hall again.
Andy