Bob, Last time I took apart a VW, and Corvair, they shared the same con
rod. Not sure about aircraft engines, but pretty sure the one in the C
150 and the C 172's are not boxers. So I think you have the definition
right, just misinformed about the commanality of boxer engines. They
are uncommon enough that the manufacture makes a deal about the engine
if it is a boxer, such as Ferarri, and BMW(?).