I finished fitting and positioning the two bottom flanges on the left side of the firewall. I then began the process of drilling the flanges. I use plenty of cleko clamps to keep the flanges from moving. I worked my way up the side and after a while the last set of flanges were complete.
Before removing the flanges I made sure that they were numbered so they would end up in the same positions.
I removed all the flanges to start the deburr and countersinking process.
