got a few cracks in a lath and plaster ceiling in my bathroom the rest of the ceiling feels sound have thought about re boarding but the ceiling has a skiling (raked) in it. So question is can I just skim over the ceiling or should I re board if I re board how do I reinstate the curve and do I just taper the edges of the board wher the skiling is. If ok just to skim over the top what prep will it need as has previously been painted many thanks in advance .