Boy you are harsh.
He may have meant in total given all the airframe and engine mods. Umlimited Clipped Wing Mustangs are not an unknown since the late 40's, it has been done many times. Maybe not as dramatic as this, but my guess is he is not the 1st to clip that much off. On top of that the Leeward family if I am not mistaken is not new to Mustangs or Racing at Reno.
Notice the Flow Fence to make the Ailerons more effective or are you not familar with aerodynamic design.
I don't know what the shakeout will be. I don't want to tell people they can't have their entertainment, but they need to be better informed about the risks rather than the potential showmanship. Aviation buffs need to examine their blind enthusiasm for their hobby. You might discover how obnoxious all this sharp-elbowing and "don't dare touch my dream of touching the face of God. Or something."