Awesome stuff Lane, I used to draw a lot like this before I had a computer!
I still have many pens and sketch pads, I love fine point pens, especially Rotring, but Staedtler and Pentel too... my smallest Rotring was 0.18 mm... but 0.25- 0.5 was more common and practical for me. I recently resurrected my old Sheaffer fountain pen which is nice for little doodles, as well as writing of course!
You have inspired me Lane, thanks man!
J