I've been trying to put a Pilot Parallel nib unit into a Moonman M2. Easy, right? There are lots of pictures and guides online.

Only...they don't work for me. From what I understand, you friction fit the Parallel nib unit into the M2 section. No go. The Parallel nib unit just falls out, there is no friction. I've tried pushing the nib unit really hard, to friction fit with the inner threads of the M2 section, but that doesn't work - it just won't go and I'm afraid I'm going to break the Parallel feed.

The Parallel nib unit won't go into the M2 nib unit, too big. The Parallel section won't screw into the M2 body, threads are the wrong pitch.

What's going on? Do I have a miniature Parallel? A giant M2? Does anyone have a good video showing how this is done? I'm at my wits end, I'd really appreciate some insight. Thanks!