I love the soap stone and how you stacked them. It looks like a natural formation. I saw you plan to add giant hair grass (GHG). I added mine to a dry start and it did well. Only thing I would recommend: If you want the GHG to stay localized, you should think of putting a barrier in the substrate - like a pot. They send out a lot of runners and they can travel a long way! I wish I had.
Oh, I know what you mean.. I have it growing in my garden and it's taking over.. I'll just have to do some aggressive pruning.
I'm hoping the GHG will mix well with the crypt. I'm following the ideas of flower arranging. Mixing plants are important and is rarely done in aquascaping. The key is to have a dominant plant and the mixed in plant acts as an accent.