I thought it was 'plywood'. I may be wrong.
I watched today's video. I see that you varied the exit gap 20-40mm. I'm curious about the ratio between inlet and exit. At the low end, I'd expect no differing result. At the high end (wide ratio) I'd expect the duct to choke off and be ineffectual.
Will you look at the ratio and magnitude. The OEM air curtains always look small to me.
Have you looked a the work Viktor Schauberger did with trout propelling themselves with water through their gills?
duckduckgo.com/?q=shauberger+trout+gills