Thanks for responding. I thought about the stretch problem when sewing two bias edges together (part of the reason I want to break the grain direction rule). But the square will be turned on its point (so, it's actually a diamond) which means the grain direction will not match the rest of the block (diagonal relativeto the other pieces). Since it's small and in the center of the block, that won't matter too much, will it? (I wish I had a picture. these things are hard to describe in words.)
Thanks!