I decided there wasn't enough overhang with the cowl attach flange at the areas where they are relieved for the bend in the firewall, so I riveted the old flanges together in situ and then used them as a template for the profile new two-piece flanges joined at the the top (instead of thirds joined in two places). I made the new flanges out of 7075-T6 for extra stiffness.
Unfortunately, I made a mistake today by drilling the intermediate holes in the boot cowl - actually I do know what I was thinking, but knowing I have to fabricate a new boot cowl is still painful!
