About the nib swapping, just as reminder, we use different feeders to control the ink flow of stub 1.1 vs others B,M,F,EF.
Stub 1.1 feeder got slightly heavier ink flow, so please don't mix up these two type of feeders. Cannot tell from the look outside, but you should be able to see the different in writing.
Thanks for this "heads up" Speedy. Fortunately (as I mentioned elsewhere), it has not been a problem for me.
RE FPR STUB NIB
The Twsbi italic nib on mine was a bit 'off' - I should have got a replacement but I decided to 'fix' it myself. In the meantime I fitted a FPR fine stub nib in it's place - the FPR nib is really very good indeed - excellent flow & form etc. The Eco is a bigger pen than I expected BUT if feels, handles, and looks (white 'top & tail' with Diamine Amber ink in) great. The piston mechanism works exceedingly well. It's much better than I expected - a big thumbs up (so far).