Originally Posted by
skyshack
Mustang just like all BMW coupes (E31 excepted) is a 2 door saloon, just park it next to a S14 the difference is an easy to see 3". Not so easy to see 1" height difference on a big long car like a XKR. Mustang has a higher "saloon" roof line 54.8" than 910 Bluebird hardtop coupe 54.5" (also pillar less) but that's no S14 either. Nissan did try, 910 saloon had 55.1" roof height. So frankly the Mustang is much more a Bluebird 910 hardtop coupe with a big engine (Ok in 1981 the 910 hardtop coupe was like a wannabe Mustang with a little baby engine).
Classic air cooled Porsche 911 set the benchmark for "sports coupe" at 50". They exceeded it at 52" when 911 went water cooled. But the more you pay and more hardcore the spec the lower they get, so some are now down to 50".
S13 and S14 just need a 20mm drop to hit that benchmark 50".
Just re-scaled a bit, mainly bonnet length. Something has to give and I think it's the back seats lose leg room like an Audi TT. When you get a 2 door saloon you can be reasonably sure that you get back seats with leg room, once you drop below 54" like a "sports coupe" back seats become a lottery.
There are other factors to "sports coupe" styling. 2nd to roof height is the flank height at front wheel arch to peak of bonnet in line with front axle. The XKR X150 is razor sharp like the S13/14 while the Stang and (most [1]) BMW 2+2 coupes show yet again that they are 2 door saloons. Again Porsche set the benchmark with ease as without an engine the wing height is set by headlamps and scuttle.
The devil is in the detail. A sports coupe has to be low and sleek. S13/14, 911,and XKR tick the boxes, Stang and BMWs don't, they are high performance 2 door saloons.
[1] There was one that was nearly quite sharp but as they had all badges removed I was never able to ID it. It may have been a 2 door 5 series but I wouldn't know.