72) Remeber the first rectangle that we used with the Loft tool? Select it and make a copy. We are going to create a cover for the botton of the seat.
73) Copy created, select and use Extrude modifier on it.
74) Now we have the border and the cover of the seat, let's now create the seat it self. To do this we are going to use a Box Primitive, create one and convert to Editable Poly.
75) Apply a MeshSmooth modifier with value 3 in Interations. Ok, we've broken the box looking but now we have a sphere looking.
76) To fix this, go back to Editable Poly root and create some aditional edges to sustain MeshSmooth interations.
78) Now it's up to you to resize the polygons of this seat to get close of the border boundary.
79) After a few tries, I got this shape below. You can do this with a ChamferBox Primitive, but I don't like it Smoothing groups.