stiffening of a convertible

[Stuart]

I've converted my 1303 1979 convertible to 944T brakes all round with Kerscher coil over's on the front and a coil over setup from Remmele at the back. This setup is awsome!! My beetle sticks like glue to the road. There is only one downside. As the suspension is a lot stiffer the car want's to twist about its axis on sharp bend/corners. Is there a way to stiffen the car. Will a bar between the front shocktowers help? Maybe a cup brace on the rear? Help/advice welcome