Jako - haven't used the vertical fibs so much (not that I have...

Jako - haven't used the vertical fibs so much (not that I have anything against them) If I did use them I would be looking to place Action lines on them - left of a centre line - and then seeing if I could mirror them with reaction lines on the right. But using this method I would normally just use sight (rather than fibs) to pick logical pivots left of the centre and then project the corresponding reaction lines to the right.
Having said that, sometimes it can be hard to make a judgement call as to an exact placement so after seeing what you've done there I might experiment.