the question isnt too clear,but i think you need to draw a level line with a spirit level from the good walls around the bad walls and where the cieling is curved you are going to have to fill the gap with your adhesive.just keep it looking straight on the walls as much as possible so your corners line up.if you dampen the walls with a fine spray of water when you stick one side of your coving up the adhesive might still be wet enough when you stick your other side up to adjust the corners to match each other.thats the best i can do with limited info.hope it helps
phil holmes, August 2009
