Now for the wing! Started with an inspection of all the bits and came across this unusual looking rivet. I didn't like the look of it - thought it was corrosion of some sort. Photgraphed it and sent the pictures to VANs who assured me it was a post anodising "touch up " of a rivet. Makes sense so feel confident to go ahead. VANs are really good in turning around any questions like this. Usually within 24 hours unless it is a weekend when they answer immediately they are back on deck.