In my case, I have installed Windows 8 EFI bootable, it created a FAT32 EFI boot partition and I try to make Sabayon 13.04 installer to recognize it and install the boot loader there. It doesn't. It asks me to place grub on MBR or Sabayon's root partition (I use one partition for all, root, home, swap etc.). Then, it seems to messed up the EFI partition anyway, as there is no Windows 8 boot anymore.
Any hints? Could the Sabayon installer be handled in a different way than MBR mode in order to boot in EFI mode, as Windows needs? Could I place it on a flash drive to alter it and make it properly handle the EFI boot?