I got another deal on an S1C, this is a complete airplane that I hope to fly for a year or two before restoring it. It's ugly but it was a much better head start being a complete airplane than my other C. My other C has a firewall shape that looks identical to the Steen plans that came with the other two projects. My s1s and this new C has a slightly different shaped firewall. It's flatter across the top with shaper radius in the corners. I haven't had a chance to pull dimensions but I can only assume these were done to better fit the cowl around the engine. Any idea where the dimensions for this style firewall would have come from? Maybe a difference in Steen vs Aviat plans or purchased component. All three airplanes were built in the mid 70's.