An exception to the holding rule is made for the cutting competitor. There was a time when no cutter held on to the horn. That was 40 years ago. Now, the horses move so fast, stop so hard and turn with so much centrifugal force that without holding on to the horn, a rider would be whip-sawed into the dirt. The back of the saddle seat supports the cantle.
Stirrups come in a variety of shapes.
Wide ones are used by ropers who stand up while throwing a loop, while narrow stirrups are favored by cutters and ranch cowboys. Something in between works for everyone else. The seat is another important consideration. Roper and rancher saddles have seats that slope slightly backwards. It is a phrase that could be used today.