check it out:
http://xiaomi.eu/community/threads/5-5-8.27542/page-8#post-246332 (((( post 155 ))
http://en.miui.com/thread-118955-1-1.html
I have done so I got miui v5
I tried .... it took me a while but it works.
reported the cell has two partitions with v5.
fastboot used with...