Topmost plate structural?

[hubrigant]

I'm going to put belt tensioners on my RoMax, as I've yet to get the belts aligned right with the lift-with-screwdriver method. Several of the options I've been considering seem as if they'd be easier to work with if the topmost plate wasn't in place.

Is the top plate structural, or is it basically decorative? Will leaving that plate off lead to vibration and/or tower alignment problems?