I am installing porcelain ceramic floor tile in bathroom. House is 40 years old. Sub flooring in good shape consists of 5/8" plywood mounted on 1x6 boards layed over joists. Since the base looks very sound, I am using 1/4' wonderboard as a backer for the tile. My question is: I plan to use modified thinset and then use 1 5/8 screws 6-8 inches apart. Is it necessary that I mesh tape all the seams? I am a bit nervous about creating "humps" at the tape seams and cause cracking pressure on the tiles. With a solid screwed in procedure is it ok to simply fill in the seams with thin set and smooth to the surface ...I plan to do that at wall edges.