Riveted the component parts to all of the ribs. Some of the 4.8mm rivets have not formed well so I will drill them out & redo them. I have since discovered that if I hold the nose piece of the rivet gun as hard against the rivet as I can without damaging the material, the rivets form much better.
P.S. I write this after having clecoed the ribs to the spars when in the jigs. In hindsight I would not rivet the "bottom skin support angles" to ribs 4, 6, 8 & 9 at this stage as they will/may need adjustment later.