Cutting ceiling Cornice

Hi,

I would like to remove a section of the ceiling cornice as I am attaching a pipe box to the wall. What is the best way to cut a small section from the cornice (plaster cornice) as it is attached to the ceiling.

Should I do this or just cut the wood to fit around the cornice.

Sorry if the question sounds idiotic...

If you cut your cornice to remove a section then you risk bringing down part of your ceiling that is attached to your cornice, too.

You eliminate that risk, if you cut the wood to fit around the cornice...