You completely missed the point. As far as Witt's testimony is concerned, the only important definition of Grassy Knoll is whatever he thought it was..
"Whatever he thought it was"? Now you're getting into Bill Clinton territory. Please stop dragging this out.
(1) Witt testified that he was walking straight toward Elm St. (2) He ID'd himself as being in the photo showing him and The Cuban sitting on the retaining wall after the kill shot. (3) He testified something along the lines of, "We just sat down" following the kill shot. ALL of this clearly shows what section of the "Grassy Knoll" Witt was referring to. It helps to be familiar with the entire Witt HSCA Testimony.