It was fun to watch you guys try. I guess it did not work out. I agree the only chance to have extra useable space is that the manufacturer actually disabled a part of the disk, and enable the part that being disabled will bring out more space. Like WDJB are made of 40GB each, so the 80GB(2x40), 120GB(3x40), 160GB(4x40), 200GB(5x40), and if they actually make 60GB/100GB JB disks, it might be just 80GB/120GB disks that being disabled some parts. Otherwise there is no free lunch. If you can really technologically make the hard drives you bought to having more space, then why the manufacturers did not do it themselves.
P.S. I am not sure the theory of disabling parts of disk is true, but it sounds like a more reasonable saying to me.