Hello krass,

I think I'm getting close to a desirable result. You can also experiment by drawing a construction line from the red cross hair to the main body. Create a sphere of the outer cap diameter. Then select all of the surfaces under and surrounding the sphere and offset those surfaces by 1.5mm. Then copy the sphere you created but increase its diameter by 40mm. appropriately fillet your edges, I think it was by 10mm on the original, G2 curvature, bulge of 1. Then you need to start Booleaning and trimming the spheres and the offset surfaces together to make things watertight. What you are left with is something that looks close to the photograph you posted of the actual cap. The reason I asked for the construction lines was I think things are a little out of square a few places, and I wanted to experiment with the transition between the generally cylindrical and squarish areas of the model. Are you working in 1:10 scale? Thanks.