After having this pen well over a year, I thought I'd just add some final notes about it. . .
I still don't really trust it with a converter. I mean, I could make it work with a converter, but I'd always feel wary and have to be careful immediately after filling it from the bottle. I trust the Karas Ink much more with a converter, since it has a larger ink collector and has never burped.
When used with cartridges the Fountain-K has been 100% dependable in all respects. I've rarely used cartridges, but I got some Herbin Perle Noir carts (high quality, unlike the cheap generic carts this pen came with!), and they work superbly in the Fountain-K.
The other thing I want to add is that the Fountain-K seals up very, very well when capped. It can sit idle for days or weeks, then I pick it up and find it writes perfectly. (This seems to be equally true of the Karas Ink.)
And... Finally, I'd like to repeat what I observed back in the very beginning. This really does seem to me like a modern-day counterpart of the Esterbrook J. It's small, solid and durable, easy to repair and maintain, dependable, doesn't cost too much. It's very much an "EDC" workaday pen as opposed to a fancy collector's item.
Edited by tonybelding, 02 July 2017 - 01:14.