6"2.5 here.
On DL650 2012 I owned, after spending money on various screens and mirrors without success I bought Givi Airflow and fixed all of my buffeting problems at any speed, no matter which type of mirrors I used, with extenders or without. At September 2014 I traded DL650 for new DL1000 (new model). OEM screen was, again, terrible. Huge buffeting. Went straight to Givi Airflow, and again, all the buffeting disappeared. Perfect again!!