I use the Koh I Nor Rapidographs.
They're a bitch to clean, but you get a great smooooooooth line. Given your skill with curve, I would actually suggest you ink with a brush. Try the Winsor Newton Series Seven Sable brushes. I use them more than the pens now.
They are very expensive, but start with one of them. And TAKE CARE OF IT, and it will last forever.
Your work rocks, it deserves to be inked.
B