MirrorMode and chaining - are slaves needed?

Hi folks,

I'm in the process of setting up about six nodes, and tossing around the idea of having either 2 masters in MirrorMode
(traffic to the "active" master is managed externally) with 4 slaves (each of whom will refer their writes to the active
master).  I'm automating some of the setup, and in an effort to simplify the configuration, was wondering if I might be
better served by simply having 6 masters with an identical configuration, each of which refer their writes to the active
master (a separate IP/hostname on a virtual interface on one of the masters).

So, the question becomes, 'are there any downsides I'm not aware of?'  It seems to me that the advantage with the 6
masters is that, aside from the consolidation of configs for the automated setup, I now have 6 write-capable nodes
instead of 2.  And, provided I chain the writes to the active master, I shouldn't have to worry about incompatible
writes/partitioning.  Any thoughts, advice, recommendations?  Thanks!

-Ryan