Date: 9/26/2008 1:10 pm EDT
If you use 80%12x12 and 20%6x6 you should be fine, depending on the layout.
I found starting in the center of the room assembling a section and moving it around to find the best balance works best for me.
Remember to layout the floor so you have at least 2 tabs on the tiles.
Good luck. It's a great looking pattern when you're done. send photos.