Hi Kamper Bob
Not sure what I can add except to say that 90% of vehicle was above 6'.
By what I know interference drag is the drag produced by two bodies near each other. Examples might be: where a wing intersects the body of an aircraft. It might be generalized by having two bodies with definite airspace between them but at some speed they act like a solid.
I felt that there was a subtantial blockage of wind under 6' where I was and where the sprayer generally was not.
Here is one with 90' of width on the sprayer. My car could drive under it easy. It is hard to visualize how big they are until you get passed by one on your bicycle. It looks like that air should move almost unimpeded under it.
