well, you can play "compressed" isos with a jtag/rgh. if you use something like exiso, it will remove the padding, and they'll be bootable. I can't recall if this is the case with god (games on demand) games, but I think it is. those are retail games you download from xbox live. some games are very tiny, but xgd2 games at least, come in sizes 7.05 and 7.29. I'm not sure of the padded sizes for xgd3 games, but it must be over 8GBs.