Lots of little detail stuff. You have to number the seat ribs 1-8 with 1,8, 4 & 5 being the most important. Deburred all those after filing the spot where you have to cut a vertical piece over a lightening hole (presumably, used in the manufacturing process).
Then prepped up a series of smaller pieces, the numbers of which all jumble together and mean nothing, but, trust me, I did it, deburred it, and riveted it all in place.
Was getting too tired to start on adding nutplates; will do that tomorrow.
By the way, on the part you see in the middle picture, Van's calls out AN426-4 rivet in three places. Too short. I used AN426-4.5 which were perfect.