Methinks you missed me pernt entirely.......
I understand accidental/lucky finds happen. I just don't believe this entertaining story as Colin would surely have been aware of Jim Hall's skirted 2J of 1970.
A Japanese friend of mine (barely spoke English), with Japanese racing magazines, told me, while discussing racing at lunch in high school in '71-2 (I'm certain, I graduated in '72 and never saw him again....you out there Mssr Itokawa?), of Chapman's working on ground effects behind the scenes........
I had never seen/heard about this via anything available here (U.S.).
Excerpted from
https://www.roadandtrack.com/motorsports/a32350/jim-hall-chaparral-2j-history/ :"There's more. To create a negative pressure vacuum that would suck the car to the ground, the car featured skirts around the rear three-quarters of the car. Hall approached General Electric to use its relatively new invention, Lexan: a polycarbonate plastic material that was light, flexible, strong, and most importantly, unbreakable. The skirts moved up and down through a system of cables, pulleys, and machined arms that were bolted to the suspension. The result was a near-constant alignment to the road surface. With the fans on, the car would hunker down by two inches.
"