You gave me a great piece of insight here... I hadn’t thought, but there was an Ion Redline that was campaigned as a land speed car, using a turbocharged LSJ to hit like 212 MPH...
https://www.wallpaperup.com/118323/2..._tuning_f.html
While I imagine that design of decklid extension is effective, it’s huge... I was initially planning 4” or so which I don’t think would require use of anything beyond a sturdy plastic(not necessarily coroplast)...