I practice English calligraphy (copperplate) as well as French, Chancellor and other Renaissance.
For my part, and perhaps you will find a start of a solution there, I use Jinhao 9019, 9016 and 1935 for their high-capacity converter - the same for these three models. Personally by adapting ultra-flexible nibs (Kanwrite and Click, but the FPR adapts to them like others #6).
These converters have a screw thread, which makes them independent of the power supply or the nib block.
If you look at one of my posts on this part of the forum, you will see the solutions that I applied:
Hole in the nib block allowing an entry of the converter while promoting sealing. Obviously enlargement of the converter orifice to 4 mm, which gives a significant flow.
I made an adapter to fit #6 nibs to the block, which allows me to adapt a large number of nibs, even old ones to dip, and feeds of various kinds: in plastic that I can sculpt, in ebonite too, in which I increase the ink supply to about the middle of the nib.
I adapted five fountain pens like that and all of them give me satisfaction, with characters that can go up to 15 mm for the minuscule body.
Afterwards I also adapted fountain pens that could do it with parallel pen cartridges.
If this can be useful to you...