This is what it looks like after it has been cut out. We made a jig. As a side note for you Jim, you want to cut all of the holes in the floor before putting any of the fenders or the hump or anything else in. Believe me when I tell you it will make your life easier. We have all of the right measurements when you get to that point.
This is what it looks like with the plate in it. The bolts that are in there are not the ones that will be there permanently, it was just to make sure it worked.
Underneath the car is a clip for the seat leg to go into. This is to allow the seat to be removed when needed. The fronts of the seat legs are hooks so you hook in the front and push down the back to hook them into place.
My Grandpa has often made the comment that most of the modern conveniences of cars can be found in a model A. Here is one of the examples right here, removable seating. Didn't realize it had been around for so long did ya?