All of this aside, the math is way off. If for the sake of argument we accept OP's claim that the universe is 1 foot smaller for the 6 foot person, we would then have to say 1 foot = 20 percent of the universe for the rest to be true. This is so far off that it is absurd. OP is wrongfully comparing the size difference between the two people (one person is 20 percent smaller than the other person) to come up with the 20 percent number instead of between each person and the universe.