Seat? Put on a back rest and handle bar risers, seat problem solved for me.

Windshield? Mounted a Firecreek Windbender, problem solved for me and the SO.

Flexing in twisties? Front fork brace, same problem on my Gold Wing, problem solved for me. PS, I added full Traxxion on my Wing, bike still flexed in the twisties, once I added the fork brace the flexing completely went away.