It never occurred to me before to find out the actual size of a DVD+R DL but now I'm wondering about it. The Gears 3 ISO is 8.13 GB. The DVD+R DL disc is 8.5 GB. This leaves .37GB of space. Shouldn't the XGD3 ISOs fit right on with no problem? Apparently they don't (which I already know). ?I'm wondering why they won't, when there is supposedly 370MB left over. Are the dual layers truly 8.5GB or are they less than advertised?