Oblique pen modified for big nibs, like Nikko G.
Made it more anatomic and with universal nib holder, don't know how much it's going to last, but worked ok for a couple of nibs profiles...
Needs some supports on nib holder round end, but works good.
Edit: for the ferrogalic ink I used:
1gr tanic acid -you can try some heavy cofee or tea
3gr iron sulphate -garden stuff
300ml water -use less if you are usin cofee or tea