The OS .15CV is, indeed, a car engine. The CVA is the aircraft version of that engine with a standard length shaft for the prop. Supposed to be a screaming engine. They claim 19,000 RPM! I originally was going to put it in a Sig Wonder that I was building but for some reason I lost interest in the Wonder in mid build. Fuse mostly done, wing built. Dont know why, just quit building on it.
I also have a couple MVVS .15 engines handy and might use one of those on the Shrike instead of the .15 CVA. Ran in an MVVS .26 recently for a Penknife I am building and if the .15's run like the .26, WOW!
Got a couple of builds to finish before considering the Shrike so I have time to decide.