This thread will be to discuss the possibilities of some of the Rokushiki techniques. Imagine that there is either a human with the physical strength to perform these techniques, or a just a machine that can put the technique in practice.
Geppou, not possible. With the fastest and strongest kick you would just being send more force and weight downward, making you fall quicker.
Shigan, call me crazy, but this should be possible. To get the velocity of a punch, you would take the speed and multiply it by the weight of the punch. You would then take the velocity, and divide it by the size (inches) of the fist. You would then have the force per square inch.
So say you have a punch with the velocity of 200lbs, and the area of the fist is 12 inches, you would be getting around 16 pounds per square inch. The velocity will stay the same but using the finger, which has an area of say 1 inch, you would be getting 200lbs per square inch.
The only issue, would be making sure the bone structure in the finger could take that amount of force. As long as the finger could stay straight, and take that amount of force, Shigan should be possible.
I will post some more later.