[David70]

If I was adding a roll bar to a street car I would make sure there wasn't a chance my head would hit the bar if the car is hit from behind. Someone hits you from behind and you aren't wearing a helmet and it is like getting hit in the back of the head with a baseball bat. Add foam around the bar and it is like getting hit with a baseball bat wrapped in foam. I also think my chances of getting rear ended are far greater than rolling over.

If you want the roadster with a roll bar because you want a convertible and want track ability it might make sense, if it is to save money I don't see coming out ahead long term. Buy the roadster and go through the cost/process of adding the bar (including modifications to the interior to put it in) which then reduces the resale value and the end result is unlikely to save you money long term (also considering resale).