In a pakal knife fight, you do not square off with the attacker and have a lengthy duel; you use deception, feints, speed, ferocity, and controlling tactics to end the confrontation as soon as possible. Since pakal uses a lot of thrusting and ripping, a short blade held in a reverse grip is the best weapon.
You may pull against the edge of any blade with much more force than you may push against the edge. Attackers are not usually naked, they wear clothing, and depending on the situation and the time of year, there may be many layers of clothing or heavy clothing. It is difficult to cut skin through all this protection. In a forward thrust, the defender is usually moving backward away from the attack so it is difficult to penetrate the clothing, even with a large blade. However, when a small blade is pulled inward against the person's body, it is easier to penetrate clothing since the clothing is now backed by the firmer surface of the body.
Because of clothing and the flailing movements in a fight, the short knife has less a chance of getting snagged or trapped. In a thrust, only a small portion of the length of a large blade will penetrate, so it is difficult to get enough leverage on the handle to control knife. A short blade may penetrate to the hilt, but this gives the user tremendous leverage for pulling and ripping. If a large blade penetrates too far or strikes a bone, it may become lodged and difficult to remove. The added leverage of a small blade aids in its release from the same situation.