Just thought I'd point out something for consideration in Laguna2's calculations.

Mike J Wilson's animation and comparison (to the video imagery) seem to indicate that the 757's apparent length was about equal to the apparent width of that gate control box that just about obscures it, length-wise. The calculations indicate that an object up to 40 meters long (based on the assumptions) could be obscured while the apparent 757 fuselage length would be about 27 meters. This would make it seem that the 757 fuselage apparent length should be (pictorally) about 2/3 the width of the gate control box which does not seem to be a match to Wilson's animation.

I stopped by a parking garage near my work place and took a rough measurement of the gate box. It would be approximately 15-16 inches square. The cross dimension would have been approximately 20 inches or so. I don't dispute your research saying that the best information you had said it was 0.8 meters (or about 0.57 meters square?), just pointing out what I found. I would admit that the gate box in question seems bigger than the gate mechanism nearby, just not sure how much bigger.

I pretty much agree with the overall calculations made. I am pointing out that, despite the assumptions that have to be made barring actual field measurements, a skeptic (or CTer) might point to the discrepancy between how wide the 757 would appear versus the gate box, and the animation Wilson did and claim that you didn't prove anything.