Convert Waterman Phileas from Rollerball to Fountain Pen?

[Peony Blush]

I have three Waterman Phileas pens - two rollerballs, one fountain. Does anyone know if there's a way to covert the rollerballs into fountain pens? Although I have other beautiful pens, the Waterman Phileas fountain pen is my go to, workhorse pen. I never use the rollerballs. 

 

Although they look like they would be, the innards of the pens are not entirely interchangeable. When I put the fountain nib assembly into the rollerball body, the the body doesn't screw on all the way. I suspect if I used a smaller cartridge or converter, it would work. Has anyone tried this before?

 

(This is my first post - I hope I did it right!)

 

[Peony Blush]

I just noticed the second photo resembles a police lineup! 😄

[OCArt]

I suspect Waterman put a metal plug into the tail of the pen to add some weight thereby making the inside chamber too short for your long ink cartridge.  Have you tried using a short ink cartridge?

[Peony Blush]

3 minutes ago, OCArt said:

I suspect Waterman put a metal plug into the tail of the pen to add some weight thereby making the inside chamber too short for your long ink cartridge.  Have you tried using a short ink cartridge?

I have not! I'll give it a try. Thanks!