Cabriolet shells don't handle as well. They flex alot more and you will get scuttle shake, in some cases resulting in the paint on the scuttle panel cracking due to flex. I've seen this on more than one RS Turbo conversion.

Buy a tin top mate, it's a proper RS and will handle so much better. The only way to get a cabby to handle properly is to have the shell braced. That's expensive and will look 'orrible !!!