Concur with the octagonal passages, disagree with splitting it into quarters. Splitting the cannon directly along the plane of the magazine introduces a very large joint that is a potential weak point, requires significant effort to seal, and may cause problems from whatever you use to seal it. Even solvent-welding isn't certain, because you can still get ooze that blocks the passage after you've inspected the part for satisfactory printing. Not worth it, just design passages that print better (hexagon/octagon helps) and use a larger ID if necessary. Also, if you're doing this much printing, it may be worth looking at your own 3d printer. Printing at a local shop is fine if you're doing small scale, but going through a complete development cycle on a complex ship like the Surcouf is a lot of print time. Imagine how much nicer it would be to print overnight or while you're at work.