Well, I’ll give the explaination a try….
The theory is based on the though that the pull or tension you feel is your pc muscle pulling on the tunica. The hinge point for the tunica is lower than the hinge point for the ligament. So at any point on the “clock scale”, if the tunica is shorter than the ligament, you will see the tension or pull-back. Since the tunica hinge point is lower than the ligament hinge point, the farther down you go on the clock scale, the length of the tunica begins to equal to the length of the ligament, until the tunica is shorter than the ligament. If you lengthen the tunica, then the point at which the tunica distance to hinge becomes shorter than the ligament distance to hinge will be higher on the scale.
Do this… put your arms straight out in front of you, and clasp your hands together palm to palm. You will notice that there is some distance between the “hinge points” of your arms, namely your left shoulder and right shoulder. Let’s say that your left arm represents your tunica, while your right arm represents your ligament. Now imagine that as you move your hands toward your right side, that represents getting and errection, or moving your dick up towards your belly, while moving your hands to the left represents loosing and errection, or moving your dick towards the floor.
Without rotating your shoulders, move your hands to the right. You will notice that while your left arm can be straightened, your right arm cannot be without unclasping your hands. Therefore, the limiting factor of how far your hands can be away from you is your left arm (tunica). If you move your hands to the right, the limiting factor becomes your right arm (ligament). If you lengthened your left arm, you could move your hands further to the right before your right arm bends. So in effect, lengthening your left arm (tunica) raises your LOT (loss of tension on the tunica) a few “hours” on the clock scale. If you reverse that, and lengthen your right arm, then the opposite happens, and your LOT moves a few hours down on the clock scale. You exact point of LOT (loss of tension) is actually a point of equality, where the length of tunica and ligament from the body become equal. As long as the ligament is longer, you have tension. If the tunica is longer, you loose tension earlier.
I wish I had a graphics program here at work so I could draw you an illustration, but maybe that explaination will help, although I wouldn’t call it a “simple” explaination.