Chris, thanks for the nice words! I overlaid the design on the photo and blurred the edges of the mask slightly to make it blend better. I think the pixel view made it a lot easier to trace the shirt, than if I had to do an approximation with only a vector line. One of the features I found really nice from the introductory video on the AD website.
Nils, thanks for having a look at the project! Yeah, those are all closed shapes. For the middle and bottom part I used the polygon tools, that are already available, so they already produce closed shapes, but for the top part, where I used the pen tool, I made sure to close all shapes. It's something I have left from working with advertising agencies - non-closed curves means bad news. It applies mostly to plotters or laser-cutters, but it can cause issues if you export your art for other vector or 3D software such as Blender as well. Obviously not a 100% necessary thing to do, depending on what you do with your artwork, it's just a habit I have.