depends on what kind of look you like and sometimes the design you select. Here's a couple of my 6/8/12 cakes just to give you a visual:
http://cakecentral.com/modules.php?name=gallery&file=displayimage&pid=1232880
http://cakecentral.com/modules.php?name=gallery&file=displayimage&pid=1432833
Depends on the design probably. If you plan to fill it in appropriately with maybe flowers or something it might be ok. If it's a real sleek cake say with only ribbon or something it might look funny. JMO
If you're concerned about symmetry, could you go with a 6/9/12?
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