Before they finalize the shelf design Willie and Tony need a volunteer - a young lady to sit on the seat naked and reach for an imaginary soap bar on the upper shelf. This is needed to ensure the seat and shelf heights and distances are correct. The young lady should be a musician, because this job doesn't pay very well, and you're likely to get screwed by the person who hired you. A musician would be accustomed to that kind of treatment.
Progress is being made. Positioning the tiles diagonally and with a border adds significantly to the installation time.