I have usually waited until September or later to take divisions however after a bit of observation, I have noticed that divisions with new culms seemed to do well.
These are all 1 culm divisions. In preparing for the divisions, the first thing I did was water the area thoroughly a couple hours in advance to make sure the soil is loose. I also applied wilt pruf so that the leaves do not transpire very quickly.
I took 6 divisions total, using mostly 5 gallon pots with old leaves on the bottom. I made sure most of the soil stayed on the root ball to minimize the transplant shock, then filled in the rest with my home made potting soil, and I also added some of the transplant myccorhizal powder to help further reduce stress.
I moved these guys to a nice shady spot where they will stay until they are established, and then I'll move them back to full sum. Based on my experience, these guys should be successful divisions, but how quickly they fill out their pots is still unknown.