They can be really.brittle, it depends on how hard the flaunching is. I've roped the top across from the scaffold to steady them when working alone.
Have you got a ginny wheel on the scaff to lower it down?
Think my mate has one, but just want it off the chimney if it breaks on the way down so be it, as it is just sitting on top and am removing the flanching to the other flue as it has been sealed over, so the plan is to put two smaller pots on..