Dog Box for my Tramp

The trike is a Tramp- my dog is a scamp. I’m planning the build of a faired container and cargo box to support our dog and gear, to sit atop the existing fiberglass fairing. I’m thinking to connect the box to the existing rear seat hardware, and wonder about a transition material between the trike fairing and the box. Most confront this by leaving an air gap, but I wonder about employing a rubber pad or gasket- thoughts?

I think this is the model Lee H Mann had said doesn't take kindly to weight on the rear. You might want to see if you can find a weight limit for that trunk. Unfortunately Lee's no longer with us.