I found this thread because I am also interested in upgrading to DSM 6.1 and am already at DSM 6.0.2. I was comparing the grub.cfg files between v1.02a and 1.02b, and unless I am missing something, there is a critical omission in the v1.02b image and grub.cfg. v1.02a contains three directories on partition 0; EFI, grub, and image. v1.02b contains only EFI and grub on partition 0. Also the grub.cfg on v1.02b is missing the references to any boot image. As a result, booting off that image results in the bootloader screen constantly cycling since there is nothing to boot into. Is there a more complete version of the v1.02b image? If not, are there instructions for adding the appropriate image to the img file? Thank you.