Welcome to- The Fountain Pen Community!

I had a couple problems I was trying to get around and after getting a Marlen while I was in Rome this is what I came up with.
The Marlin is on the left.
The yellow one is a very soft material that did not hold external threads worth a darn but internal ones were fine so I made up the section that also holds the cap and body together.

The green one was a different problem as he wanted to use this section as a highlighter pen but it had to use the Pilot pump converter.  The problem was the converter was thicker than the threads that I needed for the section. So this way the nib section is sealed into the thread unit and the converter is installed from the rear end of the pen.  So you install the converter and then screw the whole unit into the pen and then you can screw on the cap.





Hope you all like.