Exactly what you said. Side deflectors or Lower deflectors. When I first got my batwing installed I had a very similar problem and it was due to the air coming around the lower section, hitting the tank and my legs, and being shoved upward. You can get fork mounted lowers to help with this, or even a wider windshield itself. For the batwing they have a specific part when lowers fit on.
As an example:
http://www.cruisercustomizing.com/batwing-fairing-various-metrics/part/MEM7031?source=igodigital (The lowers are the small windshields you see mounted on the "bottom" of the batwing.
http://www.cruisercustomizing.com/memphis-shades-universal-lowers-plastic-only/part/MEM-LOWERS (As a fork mounted set.)
http://www.cruisercustomizing.com/s...s-front-fork-deflectors-clear/part/BBP-51-328 (Better Picture for clarification.)
As an example:
http://www.cruisercustomizing.com/batwing-fairing-various-metrics/part/MEM7031?source=igodigital (The lowers are the small windshields you see mounted on the "bottom" of the batwing.
http://www.cruisercustomizing.com/memphis-shades-universal-lowers-plastic-only/part/MEM-LOWERS (As a fork mounted set.)
http://www.cruisercustomizing.com/s...s-front-fork-deflectors-clear/part/BBP-51-328 (Better Picture for clarification.)