Heuhen, I've checked your numbers off of the drawing, and well, you've bracketed the true values very well. The Turret should be 31 pixels while the turret+Gun should be 63 pixels. The deck level to the top of the sighting domes should be 28 pixels (this means that your large one is one pixel too short).
Please don't get me wrong, I really like the work, and if pressed, will take the large one (I'll shorten the barrel though).
I think i can re-size it a bit! if you don't want to.