Hi guys. I'm back after a terrible few years with my partners health. She is improving slowly. Got a neck aching job to do. I would like to know what trowel and adhesive you guys would use to lay 6"x 6" porcelain tiles on the ceiling. I was thinking a 4 mm notched trowel with a rapid set flex adhesive. I will be putting a backer board up because the ceiling is skimmed. Could I use durabase matting instead? Should I wear my motorbike helmet whilst tiling. Just like to say this is a brilliant forum and I enjoy every ones input.