Just a warning to anyone else who thought that flex nibs looked interesting and, like me, didn't realize the requirements of needing to use one with existing scripts. Maybe this is obvious to a number of other people, but it wasn't to me.

I like the look of Spencerian script:

I figured, hey, I'm using a fountain pen, which unlike most other writing instruments, can take flex nibs and with them, do variable-width lines. Why not give Spencerian a shot?

I finally got a nib that has decent line width variation, a Fountain Pen Revolution EF Ultra Flex, and put it on a pen, and started practicing letter forms.

I promptly sliced through the paper. Repeatedly.

I took a closer look and realized what was going on.

Usually, when writing in cursive, the pen is at something like 45° from the line of text. I was doing the same when trying to write in Spencerian.

If you intend to write in Spencerian or Copperplate script, the nib must be perpendicular to the line of text, so that a vertical downward stroke is pulling directly towards the pen.

The calligraphy crowd typically uses dip pens that amount to just a nib, and can stick the thing in an oblique holder, so they can have their hand at a 45° angle to the paper, like normal, but still keep the nib aligned perpendicular to the line of text.

But a fountain pen user can't do that. They'd have a huge, unwieldy fountain pen hanging off an oblique holder. If they want to write in a script that requires that nib alignment, they must rotate their hand relative to the paper, and retrain themselves to write that way.

If you aren't really wanting to retrain yourself to write at a 45° angle from normal, you probably can't use flex-nib fountain pens to do Spencerian or Copperplate or similar.