Spent all day on the second skin and the trailing edges of both. Learned a valuable lesson about keeping rivets in line - don't rely on bottom up measurements for groups of holes (e.g around pivot brackets etc); stick with the lone line or the holes end up looking like a dog's breakfast! And another thing, that rivet spacer isn't as accurate as you may expect! Not to worry, I kept the required edge distance so it will be structurally sound.
