I've been working a little on the Giant, but haven't accomplished much except for some deep thinking about whether or not giant-sized humanoids would be possible in the real world. Most of my thoughts are centered around whether human body structures could support themselves when blown up 5 or 6 times. Could the skeleton support its own weight? Could hollow bones like a bird's or dinosaur's bones support the giant? That would cut a lot of weight out of the giant's total weight. Would joint problems be an issue? Would the various membranes be able to hold the organs in? How would blood circulation be with so much area to cover? Would the giant be able to find enough food and drink to stay alive?
I've also been considering the various roadblocks to the evolution of giant-sized humans. Usually it seems that organisms evolve to meet a certain environmental need, such as the moth species that moved from predominantly light specimens to mostly dark-colored individuals after the Industrial Revolution covered everything with soot and made the dark moths less visible to predators or the bird species that developed different beaks based on what food sources were available on their islands. I can't really think of an environmental need that would make humans grow to large sizes. The only advantage to being giant-sized would be that you would be bigger and stronger than potential predators, but humans seem to have gone with technology solutions rather than brute force solutions.
I haven't come to any real conclusions, but it seems that giant-sized humanoids would be inefficient and suffer from arthritis unless they developed slow metabolisms and lightened skeletal structures. There seems to be no reason for humans to become much larger than they are now.