Thanks! Here's the fit:
Wow, that's a lot of height to make up! I almost want to just stick a vertical board there to see what will happen. Or better yet, a couple of boxes. But I'm in a hurry, so I'll just make an arch-shaped spoiler.
When I make the arch, do you think I need to leave the tunnel clear, or do you think it might benefit to block it to encourage the stationary vortex, so the air knows to go above and around?