Not sure of the entire size as I played it on my RGH and not a flashed console. On other sites people say using Horizon to transfer the files from disc 1 onto the hdd works. I guess they extract Disc 1 data inject it to Xbox 360 formatted USB then copy to HDD. Perhaps that will help you in this case.
make sure you clear your system cache and delete all corrupted save data
if that don’t work I also burn a new copy it was ran through ABGX with the new ini file and I clear system cache after everythingit worked for me hope it works for you honey boo boo
If you can’t figure out then just open the ISO and open CONTENT and then there’s two files in there and just open them in horizon and save to device and transfer them to your hardrive.