I replaced the tuners on my fender '62 RI Jazz with a set of HB2's. I didn't notice any difference in weight as I tried to find tuners of the same size as the originals (same hole positions). The reason I wanted to replace the tuners was not the weight but I thought the original ones sucked.
If you want to lower the weight you need to get smaller tuners than the existing ones, otherwise there won't be much of a difference I think. Unless they new ones are made of titanium...
