This is not a hijack, we are still on topic, as everyone will easily point out that one difference between radials and inlines is the frontal crossection area. The "frontal area means drag" often comes up in such debates and I wanted to point out that frontal area has little to do (directly) with drag. Surprising maybe, but this is physics. It is the big hole in the center, the edges of the rim around this hole, and labyrinth of airflow through the engine that makes the difference - also known as "cooling drag".