Hello guys, this is my first reply here.
I am building a "Pensa-Suhr" and I had the same problem, but I could sort it out, although I am thinking about new ways to do it.
For doing the headstock binding I first did the binding channel with a gramil. I was a bit worried but after all it was not difficult at all. The gramil allows you to do the channel on the curved part after the nut (what you call "3d").
Then I had to glue the binding, and this was the most tricky part for me. I had to discard lots of binding plastic.
Bending the "2d" part was not hard, but the "3d" area was complicated. I tried with boiling water but nothing happened.
I ended up heating it on an oven burner (as well as burning my fingers, hehe). Note that I did it in 4 different sections.
Here are some photos, and please tell me if you come up with another way to do it.