I have a strake on my IVP piston but I am still trying to figure out how the air flows around it.
Looking at it from behind the plane, you can imagine the air flowing parallel to the fuselage, which at the point of incidence with the strake is NOT parallel to the strake.   I wonder therefore if there is more drag there than would first appear.

That is why I am wondering if anybody has reliable before/after numbers..

Colyn