Heavy-Lift Drone Frame Consultation

I’m developing a concept that flies a large, thin advertising panel beneath a heavy-lift multirotor. The panel must stay flat and stable in rotor-wash, yet every gram of the supporting frame and its mount counts. My immediate need is engineering guidance on how to design and attach a lightweight composite frame that carries the panel without pushing the aircraft’s centre of aerodynamics out of tolerance. I just need someone who is knowledgable about this and can talk me through whats possible/not possible, and give their best advice. Would like to start with an initial conversation and we can evaluate if we can continue working together on this. If you’ve designed airborne payload structures before, especially for drones carrying banners or other large surface-area loads, this might be up your alley.