rockville

The roll bar discussion comes up a lot on the Miata forum. Roll overs are quite rare so I wouldn't worry about this unless you plan on tracking the car. BTW, if you actually look at pictures of the chassis of each car you will see the roll over "protection" of each isn't that different. Inside of the bodywork behind the seats on the Kappa is a "roll bar-like" tube. If you look at the S2000 chassis we see the same thing. The S2000 parts are taller but appear no more substantial.
http://www.seriouswheels.com/pics-20...A-1280x960.jpg
I'm having trouble finding a picture of the S2000 bare chassis with the roll hoops installed. Here is something close
http://wallpaperweb.org/wallpaper/ca...00_09_1600.jpg

Note that neither structure is above the head of taller drivers. It's also important to point out that the pictures are not a good comparison as they show the Kappa in a ditch where even the S2k's hoops might not keep the side of the car off the pavement. The S2k is on more or less flat ground.

rockville

Here is the same Kappa after it was turned over. It appears the "hoops" such as they are didn't collapse.
https://www.s2ki.com/s2000/uploads/g...67d1839b61.jpg