Here is a link to a video i made quite some time ago with a 2080 over my tank. You can see the shadow a bit in the video(the camera does show it a bit darker then in life. But it is there). I have had some people strip off a couple rows of the optics (1 on either side of the brace) to get rid of the shadows. Some have also replaced the brace with acrylic (scares me a bit) or have gone with 2 pendant style for better coverage(but cost is a bit higher).
http://youtu.be/Y24E0WGHLNU
Just for reference, here is a video of tank at same time with 2 x d120 fixtures to show the coverage (the d120s are not programmable but it gets the point across).
http://youtu.be/mDpyHmfYjwM