There's two year past, maybe your problem has been sovled, because I used have the same prolbem with you, so I want to share my opinion aobut this problem. If there has another partition which contain a large free space you needn't clone your boot partition to other hard disk, you could use some partition software such as Partition Aassistant, Disk Director, or Gpard to resize your boot partition, if you inisit to clone your boot partition, here is also an article about "how to clone partition to another hard drvie and ensure the boot partition is on the target disk"
