I forgot to address this before drywall went up. Now everything is up and painted. Went to mount vanity light and I have the vent pipe dead center of the vanity.
Only about 1/2" between pipe and drywall.
Also no studs near by. I can't use one of those fan box's with expandable legs because it would hit the pipe.
I was thinking about cutting hole for a box then putting in some 1/2" plywood strips attached through drywall the same way you would repair hole in drywall. Then attach pancake box to the strips of plywood.
Sound OK? Vanity light is about 7lbs. Any other options?