I have been having a lot of trouble with a fin I am trying to model. Initially, the issues came from surfacing a 3 sided boundary (this is why I use the 3D sketches and it looks a little messy at times). Once it had been surfaced, I extruded to surface and mirrored body around midplane. I then had issues trying to make the holes at the bottom where they would go through the mirrored part but NOT through the surface. To get around this, I trimmed the surface in the shape of the hole. Now, the part looks exactly how I want it and it seems complete but it will only print half of the hole! I have attached the STl and the SW part as well as screenshots of cura trying to slice the piece. While it is clear there is an empty space on the part, it prints half filled in. Any ideas on how to fix this? Thank You!