As I recall, the main criticism of the Revson spoiler was not necessarily how low it is but how far forward it projects?
It is a nice design and really is more then just a spoiler. It is more of a lower nose extension.
As such, it projects just far enough to make entering and exiting driveways a certain obstacle to the things longevity. Living with it in reality on a day to day basis is the problem. For a racecar it MIGHT be a different story but if I am not mistaken, I think there was a journalist reviewer that suggested that it might be better to make it out of a more flexible material?
Back then, things like flexible plastic bumper covers didn't yet exist but I suspect that was the thinking on the suggestion?
I know that when I got my 73 Pantera, the sheet metal under the radiator support was already torn up pretty good. So extending anything down there requires the acceptance of the inevitable that any spoiler is just living on "borrowed time" and somethings gonna' get ya'?