Trace guide adjustable

In order to adjust the pen a bit more, I splitted the original part to two separate parts - they can be connected with the help of an m4 (or any other one that fits) screw.
I also changed the rounded part to a more pointy edge, in order to get in tighter corners.

I also pulled the shell a bit lower, in order to trace more flat parts of a few milimeters.
And the last change is an additional cover, which helps to adjust the tip of the pen to both edges (edge in front as well as bottom). With the help of the cover, one can make sure that the tip of the pen reaches the full front and the bottom. By pushing the pen tip to the foremost corner in the cover, the tracing will be as accurate as possible, as the tip will be parallel to the trace guide edge.