I'm not sure if this has been discussed yet, but I noticed it when I was watching RoTJ last night and it kind of bugged me. Notice in the image below the interior of the bridge on the Super Star Destroyer.
Notice also that no part of the ship is visible past the bridge windows. Now, considering just how big this ship is, it's impossible that none of the hull would be visible from that angle on the bridge. There is a similar shot later on in the film, just before the ship is destroyed:
Now, there is a large grey surface in the background of this shot, but the curvature would suggest it was the Death Star rather than the angular hull of the Star Destroyer.
In short, would it be possible to add the hull to the scenes involving the bridge of the Star Destroyer? There aren't any shots similar to this in Empire if I remember correctly so it might be difficult to find one that fits nicely.