Good luck! Can not wait to see them done.
If you have not found them yet, there are some great tutes for tumbling blocks
without the "
dreaded Y seams".
http://www.youtube.com/watch?v=DWpSETMbws4
Another one does it a bit differently but the same results (scroll down - she has three tutes to looks at)
http://scrapatches.blogspot.com/p/tutorials.html