animation at edge of pattern tiles

Any good ideas on how to make this
http://cs.sru.edu/~ddailey/svg/tiles0k.svg so that the moving pieces don't
get mucky at the edges of the pattern tiles?

 

Btw, you'll need either Chrome or Opera (or maybe a recent Safari). It
crashes Safari/Win. I suppose that what Apple would call a feature. And the
fact that the animation doesn't follow animated paths is an old Firefox but
reported years ago. I recently reminded them about it.

 

Using the thing as a part of a mask on an image is sorta cool:
http://cs.sru.edu/~ddailey/svg/tiles0L.svg 

 

Cheers

David