Shark Tank?
Good idea with the yarn.
I’ve been reading on aerodynamics. The little fin on cars diverts the air. I’m like, “Why’s there nothing for enclosed trailers? I’m guessing I’ll save $50 this trip. I read that a 5 or 6 inch fin, straight back, or turned slightly inward, is needed. Hills aren’t helped by fins, of course. I think plain old Lexan would ideal.