Here are the seat ribs after drilling and clecoing them together. You are looking from the right side.

The seat ribs form the structure under the cockpit floor. They support the seats, the seat belt attachment points (front seat only), and the control stick mounts. They also connect the carry through structures for the main and rear spars.

The end on the right side of the picture will be riveted to the back of the main spar carry through structure. The aft spar carry through structure can be seen about two thirds of the way from the right side of the picture. The little pieces stick out toward the camera are where the rear spar attaches.

The pieces running diagonally up from left to right are where the front seat lap belt attach. As of today, I've got all of these parts deburred except four, then I will prime them and rivet them together.