Tackled the port engine housing tonight.
This is another little problematic piece. It is basically a octagonal tube, but the length of the octagon caps (front and back) have side edges of about 12mm (so a circumference of 96mm), while the wall sections are all about 12.75mm wide (so a total of 102mm). Not sure why this is so, since the way I would score the wall sections would be on the outside edges, so the inner circumference would be equal to the disk I will use as a cap.
So what I ended up doing was to split the walls into separate sections, flood the edges with super glue, and then sand the edges back. I know, sounds like the last thing anyone sane would do, but there is a rationale: the front cap is recessed into the body of the engine, and the walls of the engine is quite thick (being heavily armored and all), so I made the entire thing out of 1.5mm chipboard. Trimming these pieces by 0.75mm symmetrically is easier done with sandpaper than a knife, plus I get a beveled edge so the outside diameter maintains its 102mm circumference. Maybe that is what the author intended?
Note the four small extra slits I cut into two of the sections. I'll be running wooden stirring sticks through these to support the wings, since they will be pretty heavy with armament and VTOL fans, and the joining surface is very narrow, so it will most likely otherwise be a point of failure.
Here's a photo to demonstrate what I plan:
You can see the two stirrers inserted through the slits, supporting the shape of the (to be completed) wing. Also the top hatch has been cut out, and the last of the side plating has been added to the port hull.