Once all of the ribs and spacers were drilled I removed the top skin and spent some time shaving a little material off the tops of each block. They were protruding slightly above the profile of the ribs.
Spacer blocks and ribs drilled
Top skin removed; Tops of right spacers shaved to match contour of ribs/skin
Top skin removed; Tops of left spacers shaved to match contour of ribs/skin
