The tank ribs were already drilled to the baffle when I bought the kit. Today I layed out the rivets lines on the tank skin per the drill plan and drilled the majority of the holes in the skin for the ribs. I marked the proper rivet line on the ribs to ensure proper allignment before match-drilling. I then cut spacers to go under the baffle and placed the baffle/rib assembly on the spar. Using tie-down straps, I strapped the skin down to the ribs and match-drilled the skin to the ribs using the lines on the ribs for reference.