Ok, the fleckstone action is dry to the bone. 
My thoughts - The texture is perfect. The fleckstone covered all the cracks and brought out the general shape of the window-slit quite nicely. 
The color - especially in photos - not so much. I think I'll paint it flat gray and then follow-up with some dry-brushing around the areas that water would spill down  it in reality. 
Here's some photos to show the progress...
And further, here's a nice closeup of Destro looking out over the shores of Cobra Island...
Thoughts?
Cheers! ~ Paul.