After reading the article, it sounds like open hand is okay, but belt bad.
I would think the belt would be safer, as an open hand has more mass, where as a belt gives.
Kinetic energy is equal to 1/2 mv2, where m is the mass and v2 is the velocity squared.
Since velocity is squared and mass isn't, it is velocity that is of greater importance.
The whipping action of a belt, and the ability to follow through with a swing, results is a velocity that is greater than what the arm can provide in a spank. Furthermore, the kinetic energy is applied to a smaller area on a belt than with the hand.
Guess you never got the belt growing up.
I’d take the open hand every time!
My Dad also had a wooden paddle with holes in it! My Mom eventually made that disappear one day.
We always got it with the fly swatter my Mom kept hanging over the washing machine. A lot of flapping going on but not much pain. Scared the bejesus out of you and you did tend to remember not to do the deed again. :-)