Leave it alone for now. The general rule of thumb is never to transplant during shooting season, and the second rule of thumb is to wait until it's pretty dormant, which would mean late fall to early spring.

I moved a Fargesia Robusta about six weeks ago. It wasn't very big and I was able to get the whole clump, but not all of the roots of course. It had shoots an inch or two long and I broke one of them accidentally. The rest of the shoots survived just find except one that aborted late. The clump was heavy enough that I could *barely* lift it into my wheel barrel. Since I lost some of the roots, I cut off some of the culms to hopefully balance it out. If the clump had been too big to move at once, I would have just chopped off as large a piece as possible and moved that. I don't know if it was the optimal time to do it or not but it seems to have taken quite nicely.