Great questions here guys
Stay tuned for a video to explain this descriptively enough so that it will make some sense. It's less an isometric exercise and more of a way to train your body to decelerate its distal segments as the proximal ones are already accelerating as is the case in almost any ballistic action. To understand how this works you first need to wrap your head around the concept of proximal to distal sequencing. This is really just a way to describe the whip like action the body uses to transfer the energy it creates at the ground, through the core and out to the periphery. If you think about throwing, punching, kicking jumping, spiking, serving etc you begin to realize a couple of things. First - no one throws harder by focusing on the throw itself. It is the wind up makes the difference. No don't get me wrong - mechanics of the movement are of course super key. The power though comes from the loading of the action. Secondly when we think about the throw, the foot, then the hips, then the thoracic spine start to come around while the hand is still going back. This is the proximal to distal sequencing in action. This is illustrated pretty well in the tennis serve sequence below. You can see how Sampras' shoulder continues to go back into the deceleration loading of external rotation even though the rest of his body is accelerating upwards toward the ball. In this way he can maximize his power.
So - the fixed point load technique focuses on training the load or deceleration phase of the movement. The TRX fixes the hand and then the rest of the body runs the pattern. Be sure to start off going nice and slow to begin with. Keep tension on the TRX the entire time and once you get the feel for the action you can begin to add speed.
Once you have it right you will find that it is a great movement prep exercise and a very cool concept
Again as I said, stay tuned for a video blog on it but hopefully this helps