Here's some reference pics from the Cross-sections book.
Front view.
Left side view.
Back view.
Right side view.
Top view.
Bottom view. Here's where all the major changes are. I redesigned the entire underside to give the ship the correct red line. Technically, there's supposed to be a grated vent where the red line widens, but that doesn't work on such a small model.
Another angle. I also added all the inverted white slopes. I believe they were originally grey.
The front red inverted slopes were previously dark grey. I don't know why Lego did that, but I replaced them with red ones.
Another view of the bottom.
Action scene! And yes, that is a modded Star Destroyer in the background.