I've got the pumping xenia. I've used a razor blade to slice a branch off. Didn't cut it down to the rock and try to pry it off the rock though. I used a rubber band to secure it to another rock. It may have attached sooner, but after a week, I removed the rubber band and all was well. Otherwise, they will spread right where they are and get thick. I've had mine for about 5 months and it has increased in size about 5 fold already.
Be careful of what you ask for. At my growth/spread rate, I'll be selling them to the LFS