21g - No way.
The Mustang limiting g was/is about 8 or 9 and fitted with a system to support an anti-g suit which was no doubt removed from the Ghost.
If 8 g, then design ultimate would normally be 12 g at which a wing is supposed to depart and at some lesser g if rolling.
Just cannot believe that the shortened wings would not fail at much over 12g.
Comments please from an aircraft designer or structural engineer.