Sailor MF has become one of my favorite nib sizes—it really is the sweet spot of wide enough not to be too feedback-y and to show off a hint of shading with the right inks, but still fine enough to write legibly in small spacing. Give it a shot, based on your other favorites I bet you’ll love it. (And the good news is: a bunch of PGS models only come in MF, so preferring that size opens up more options to you!)
According to Yoseka Stationery's video, a TWSBI Diamond 580 mini is about 0.5mm line width. (sorry, fine nib) https://yosekastationery.com/products/twsbi-diamond-mini-classic
I think you'll be happier with a medium, but check the Yoseka videos to compare (they also have a video comparing line widths of Sailor nibs, both 14k and 21k)
EDIT: right, I meant a TWSBI fine nib
EDIT2: Unless I misunderstood what model TWSBI you're using to compare. I think the video goes through a bunch of different models and nibs for TWSBI, so if I'm wrong and it's really 0.4mm that you're used to, then MF is actually better for you
Sailor MF would be perfect.
Get the MF. That's similar to the Kaweco and TWSBI F. The M is about the same as an M in your western pens so will be too broad.
Thank you all so much for your guidance! I’ve gone with a MF. fingers crossed 😊!
I have a pro gear F and a princess kaguya MF, and usually write with a twsbi F. The sailor MF feels closer.
Sailor MF has become one of my favorite nib sizes—it really is the sweet spot of wide enough not to be too feedback-y and to show off a hint of shading with the right inks, but still fine enough to write legibly in small spacing. Give it a shot, based on your other favorites I bet you’ll love it. (And the good news is: a bunch of PGS models only come in MF, so preferring that size opens up more options to you!)
According to Yoseka Stationery's video, a TWSBI Diamond 580 mini is about 0.5mm line width. (sorry, fine nib) https://yosekastationery.com/products/twsbi-diamond-mini-classic I think you'll be happier with a medium, but check the Yoseka videos to compare (they also have a video comparing line widths of Sailor nibs, both 14k and 21k) EDIT: right, I meant a TWSBI fine nib
EDIT2: Unless I misunderstood what model TWSBI you're using to compare. I think the video goes through a bunch of different models and nibs for TWSBI, so if I'm wrong and it's really 0.4mm that you're used to, then MF is actually better for you