Quote - Every tutorial I found so far just uses the V4 Dev Foundation instead of making fresh bones for conforming, but it seams a bit unpractical - I need only one bone after all :( Dev Foundation has the correctly set up bones, so it should be doable in Poser no?
I think I'm missing something.

The reason you use the V4 skeleton is so that the bones match exactly when conforming. It's always been the received wisdom to use at least one extra bone down the hierarchy (some suggest using back to the hip).
Any unwanted bones can be removed in the setup room, but it does require a little care, and it's best to work inwards from the extremities.