A 15' screen height is ludicrous, in my opinion. At my base there is a sea container showroom across the road from the clearway, with containers stacked up to 79' . How would a 15' screen height work there I wonder?
Screen height only covers the clearway, so you are at least somewhat airborne at the end of clearway. What you are saying is you have an obstacle in the initial takeoff flight path, so treat it accordingly...