Speeeking of Aston Martin... The Aston Martin Valkyrie AMR Pro has an interesting diffuser:
https://www.gtplanet.net/aston-marti...xtreme-enough/
It's hard to see in the thumbnails, but the outer fences are canted and diverge on the interior. I'd call them skegs. They [conform to][confirm] my own thinking.
They are also bi-plane like F1 front wings.