Those two are not different in size enough to be 2 different categories. If you've seen an FR-S in person, they are tiny as hell. The only difference between it and the Miata, is the useless backseats that the FRS has. Toyota should remove the back seats and turn that into a storage area/extended trunk space to make the car more useful.
To get much smaller, you would have to move into Lotus Elise/Smart range which isn't appealing at all for anything but a dedicated autocross vehicle.
My coworkers and I went to lunch in an FRS. 4 guys we are all about 5'10 .
It wasn't exactly super comfortable but its enough for a 15 min drive.
