I just came back from the job and I used the utility knife, scoring
along pencil lines laid out with a level. Very little dust was
produced and I now have a good opening to attach the wood supports for
the lag screws. The homeowner said he thinks he could easily reattach
the drywall panels I cut out. Once that is done I'll be able to hang
the door hardware. Still, I had the Fein ready if needed, but that
stuff cuts like cardboard.
Not bad working at your neighbor's house. It's close, and there's
always free food and coffee.
Thanks again for all suggestions,