I'm 6'3" 250 and fit comfortably in my Stalker. I have sat in a Birkin, somewhat tight by comparison. I have sat in a Caterham or two, about the same as the Birkin. Never sat in an Ultralite. I would recommend that you consider how much time you would be spending at one time in the car because running a 45 second Autox is a lot different than taking a 2 hr. cruise. I am glad I built a Stalker because I couldn't imagine spending more than 20 minutes in a smaller car. Just my 2 cents