You may be correct, but with one big problem . . . My understanding was that the plate was introduced to keep speeds below 200 MPH to prevent a car from getting into the stands. It seems to me that if Carl's car was going 230+ MPH backwards that it could've gotten even higher into the air. If it did get any higher, assuming all else was the same, it would've been in the stands.
IMHO, the problem is not with the cars. Never was. It is the tracks. Talladega and Daytona were built when these cars couldn't get around them at the speeds they do. The idea was to allow the cars to go faster; long straightaways and high banking. Heck a couple of years ago, the open wheel guys had to cancel a race at Texas because they were losing consciousness in the turns. That's because the track had not kept up with the capability of the cars.
So instead of dealing with the inevitable redesigning or closing of Daytona and Talladega, they used a bandaid which opened up the law of unintended consequences and voila, 43 cars, all going the same speed. So, yes, while the Freight Train may be a less safe condition, they are at least still mostly limited to 200 where aerodynamics has a harder time overcoming gravity than at 230 . . .
Solution? Flat corners.