I assembled the panel structure and cleco'd every hole to insure alignment. I cleco'd in the F-7109 plate and clamped the F-7108 angle. I put the forward skin on and cleco'd to the ribs and sub-panel then marked location of the center rib on the firewall. I removed the skin and moved it back a few inches then cleco'd it to the three ribs. Looking down the firewall I could check the position with my marks. I clamped the rib to the firewall along with a backup drill block and used an angle drill to match drill the rib to the firewall. Used a new drill bit, lots of Boelube and slow speed. Got all 6 holes drilled, clecoing as I went. Moved skin back to correct position for a final check that all was still in correct position.
