Here's another angle. Ford is still selling convertibles. So is GM, and most other major car makers. They don't put rollcages in them stock.
Trust me, every one of these auto makers confronts the question of how much safety is needed. They are getting sued every day over the issue. If they determine that a convertible is worthy for sale for street driving (knowing all the morons who buy their product with a death wish), then surely you can handle one safely (since you are not a brain-dead moron driving with a death wish - right?).
Now if you want to live safe then wrap yourself in bubble wrap, coat yourself in SPF 100 suntan lotion, wear a helmet when you walk out to get the mail, and for the most part don't ever leave the house. If you are not completely nuts, drink non-lite beer, eat red meat, drive a convertible, and be happy (not combining 1 and 3 at the same time).
Don't get me wrong. I'm not trying to knock on you. But step back a minute and this really seems like over kill. Forget the rollbar. Drive safe and enjoy.