Today I started the process of fitting the Skybolt flanges around the firewall. The nested flanges that Skybolt makes are really slick and I was able to space them at the recommended 3.5" spacing without much of an issue. You can start with a flange centered on the upper firewall and go from there. You do need to watch as you go past the engine mount so that the receptacle doesn't hit and adjust accordingly. The other change from the flanges is where the cowl halves split. The spacing will need to be much tighter here so I created a "double" flange which I will draw up in cad and cut out on the CNC router.