I've ridden in the back of a 911 convertible. And that was tight!I've sadly ridden in the back of a Porsche 944.
Which brings up the question of why put tiny back seats in sports or sporty cars at all?
Besides putting little kids back there (we don't have little kids any more, though we do have grand-kids), there's the big question of where to put the dog. We always have a dog and we always take it with us on road trips. As a result I've had to pass up some pretty desirable cars over the years because there was no room for both the wife and the dog. Things like a Miata and the Nissan 400Z. And if you can't take your sports/sporty car on a road trip, what would be the point of having one?