Trying to help my parents out, they're having Boxwood issues. They moved into their house and were astonished to find 15' Boxwood (more like trees) towering over them. Immediately, they issued my brother to cut the Boxwood to little nubs. Amazingly, the resilient Boxwood have grown back to about 5'. My parents now want to keep them. The problem is there are dead stumps of the former Boxwood in the front preventing new growth from covering and filling in. Would I be OK to take a chainsaw to these stumps even if they are connected to the new Boxwood?