I have a 100 year old home. 80% of the original plaster ceiling in the kitchen had fallen off the laths. My wife and I removed the rest of the plaster so that only the laths remain. We want to put in a tin ceiling (faux tin ceiling made of plastic or the like). What should I do to prep the ceiling? Is it necessary to take down the laths and then put up a new sub-ceiling like plywood or can I simply place the tiles over the old plaster laths? The laths are in very good shape and appear level and even across the span of the ceiling. Any advice would be GREATLY appreciated!