I'm 6'4" 245 lbs (193cm 111kg). I don't fit in a Miata. Literally. In the passenger seat of my roommates Miata, my knees nearly touch my chest. I don't fit well in a lot of small or even medium size cars.

I can vouch for that...

I'm 6'3'' and 250 lbs. I drive a Miata and my head brushes the roof when I drive it first thing in the morning. Come the evening however my spine has compacted by half an inch or so and I then have a little head room to spare.

Actually, no come to think of that I can't vouch for that. You must have very long legs and a short trunk, because on the rare occasion I sit in the passenger seat I have lots of spare leg and knee room.

You must be an odd shape