This is my favorite drawing pen. It's an Esterbrook J with a 9128 nib. It seems the degree of flex varies with the 9128s. It may be hard to see here, but I've got a pretty good one, based on what I've read about these nibs. I'm no expert in flex nib handling, so this is just a quick writing sample.
I've got to try and find a way to light videos like this so they're easier to see. I did this with the notebook sitting on my closed laptop. The lighting here is okay for computer use but not so great for shooting video.
Duration : 0:1:33
More flex than your usual 9048 