why are you using tapered boards? are you going to dry line it or plaster it/ if you are plastering no need for tapered boards, you shouldnt usually have a cut edge meet a tapered board, put the cuts to the corners/walls, mark out the walls and start in the middle-ish if you really need to to avoid having any cuts in line with the openings [but tbh, its not a big issue if you use decent tape] , that way all your cut boards will be in the corners, remember and stagger the joints