Yeah, technically you're right, Lane. My shoulders are above the seat back top in the Speedster, not in the Mini, although the angle of the seat back comes into play, too, in determining where your head ends up.
Leaving the Mini seat back adjusted to what feels comfortable to me, my head is still maybe five or six inches higher off the floor than in the Speedster. It just feels much more like sitting in a chair than the Speedster seat does.
The seat backs would still stick up out of the car quite a bit, though, adding to the 'clown car' effect. I think one of the cool things about the Speedster is that, from the side, the seat backs aren't visible and don't break the flow of the car's lines.
I do remember in our first gen Miata, in order to get the (tall) seat under the (flat) tonneau cover, I had to slide it all the way forward on its track and recline the seat back all the way back.