On Thu, 20 Dec 2007 10:45:53 -0800 (PST), wrote
Re Attaching 1/4" or 3/8" Drywall to Horsehair Plaster Ceiling (No
Wood):

I've done a test by screwing a drywall screw into the plaster
(which is about an inch thick), and it holds very well

Holds what very well?

As an engineer, I would want to know how many Lbs of weight it holds
before it tears out. I would want to know that for a random sample of
about 1 per each 2 sq.ft of ceiling. Then I could tell you if it would
work.