Hi Greg, I got your pen yesterday and it is perfect for me! It has just the right stiffness and flex to fit the speed I draw- not too soft and not too hard. I’ve filled it with Pelican ink and used it to draw this random drawing attached. (They are sweating because it’s very hot here in Singapore right now.) The hairlines are really extra fine hairlines, as you said, and it flexes easily to a good thickness. I would compare the feel of it to a dip pen’s g-nib, only much smoother. It’s perfect for my style of drawing! And I’m really happy with it. It will rank as one of my favourite pens I use daily as an illustrator. I’d gladly recommend you to anyone looking for affordable, well-restored vintage pens with great customer service included!