Ford has completely redesigned the softtop on its new Mustang as the automaker prepares to take on Audi, Mercedes-Benz and BMW convertibles in global markets including Europe.The top on the 2015 Ford Mustang convertible will open in 7 to 10 seconds, roughly twice as fast as the 2014 Mustang. That way, drivers won’t have to wait as long to get sunshine and fresh air. When the top is up, a new layer of insulation between the cloth layers will make the interior quieter and the exterior more streamlined.