My lath and plaster ceiling is in poor shape and i am considering putting drywall right over the plaster. Is this acceptable for a ceiling? If so what is the best way to assure that the drywall will be firmly attached? Do I have to remove the plaster? Must I attach to the studs? if so how do i assure i find them without removing the plaster? Is 3/8" drywall thick enough to prevent gravity from bowing the sheets? Thanks.