I'm not feeling the square crop, here. With a vertical crop, the diagonal line and the energy that comes with it is strengthened. In the square crop, the same line is somewhere ambiguously between vertical and diagonal, and loses much of it's energy. Also, the space on either side feels dead.
I'd take quite a bit off the sides, and maybe a little off the bottom as well.
Also, a personal take, having shot quite a bit of stuff with deep black backgrounds I am finding I like slightly more translucent shadows, with the barest hints of "stuff" back there. That's purely a matter of taste, though. Just something to consider, perhaps.