I experienced the same with the Givi screen. The Wunderlich is much better for smooth airflow, but my experience is that it flops around a lot off road. It's quite heavy too. I took it (Wunderlich) off last week and put the stock shield back on for a 1000 Km ride which was mostly off road, and was quite happy because it was hot and the extra airflow felt nice.
2009 KTM 990 Adventure