The problem could be air coming from under the screen and around the tank from below. If at highway speed you put your left arm across your chest (or if you put a tankbag on) and it cuts the buffet down, it's not the screen (or not just the screen), you may need to add lowers.
If you want something just a bit larger, consider a Clearview. They make a larger screen that will work with the Roadster screen hardware (assuming the large screen you have is a Triumph Roadster). A nice smaller screen that has nice lines is a Givi A600.
Of course if you scroll through the photos you'll see tons of screen options. Search the archives and you'll find many buffet threads.
Welcome aboard.
