Drilled and dimpled the firewall recess, then riveted the corners. Next, cleaned the firewall. Whatever tape Van's uses has a powerful adhesive; it took mineral spirits and much elbow grease to remove all the residue. Then I pre-drilled all the weldments to #30 before clecoing all the parts onto the firewall. The last step was to break apart the F-1001J parts, smooth the edges, and cleco them in place for final drilling in the next session.