Sci-Fi Gun Emplacement

My kids were looking through some old 40k books I have and saw the DIY gun emplacement on pg27 of the 3rd ed space marine codex. They asked if I could print one, so I doodled this up based loosely on the picture. I missed the rivet panels on the hillsides, but it's pretty close. I estimated the scale. It may be totally wrong. I'm printing one currently and will post a make when it's done.

I took a screenshot of the page from the codex. I don't have permission to use it, but I just wanted to show the reference object I was attempting to create.

Due to the size of the piece, I broke it up for those with smaller printers.