If I may add my 2 cents - the opening in the tunnel is, certainly, a factory opening, it also allows you to undo one of the starter screws that otherwise is difficult to access.
What I am not sure about, just judging from the picture, is if the actual cover I see is an original one (not sure if that is what Shvegel meant - was it about the whole opening/cover plate arrangement or the cover plate itself - if the latter one, he knows better than me). I do not remember now, but I think mine looked a bit different, I think it had some moulded shape around its edge... but I may be wrong.
