Adding a Back Seat?

Has anyone ever added a back seat to their car?

Here is an example of an original one

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Hey Arthur,
Yeah, looks OK, but just don't see the room for that in our cars. The shelf is not that deep at 12". You might be able to make something that looks similar, but unless the driver is really short and can slide the seat all the way forward, there's no room. Really like the idea, but see no way to implement it without major mods.

I agree with Jerry.
I too have been toying with the idea. I think, however, the best we can hope to achieve is a kind of-look-alike version.
An original backrest will fit easily, with extra room on either end. Not just because our cabins are 2" wider, but because the BN4, BT and BJ versions made allowances for foldable, then convertible tops.
So, the backrest works. It can even be hinged like the later versions; but as Jerry points out, there's just no room for a person's feet--any size feet.
My seats are adjustable (forward and backward). I'm a hair over 6' so I have the seat as far back as it goes, and I still have to squeeze in. Truth is, I could use another 2 inches, but it's just not there.
Check out your own car, Arthur. I'm betting your seat is damn near touching the lower bulkhead.
I only just bought my Saxon last September. My grandkids visited early October (ages, 6, 4 and 2). My daughter and her husband took the two older girls (6 and 4) for a spin, with their feet scrunched up in their laps.
Again, I believe you can pull off a pretty good imitation, but no way will your back-seaters sit with their feet on the deck.

That said, I'm hoping Hotrod will chip in his 2-cents (Always worth a bit more!)