It is best not to use device names in mdadm.conf at all.
Just identify the device by uuid (i.e. use the output of "mdadm -Db /dev/md0" in mdadm.conf). Then mdadm will hunt through all attached devices to find the one with the uuid given and use those devices.
If that isn't clear enough - the best thing to do is post to linux-raid@vger.kernel.org (you don't need to subscribe first) with lots of details about what you are doing and how it doesn't work.
