Here's the 12/2/71 memo referencing a redacted person from NWA that suggested the plane was on autopilot and suggested searching as far south as the Columbia.
in later search maps, I don't believe they extended the search zone to the Columbia..close, maybe as close as Evergreen. But they still focused on probably jumped near La Center..
Oh ps. There was a parachute found in Portland in Jan 1972. Cossey said it wasn't Cooper's. I've not found much detail on the parachute found in Portland. I'll include the snip where they shipped it, and when Cossey said it wasn't Cooper's.
Interestingly, there was a memo talking about hiring Cossey to recreate the jump. They decided it was too risky.
If you distrust Cossey, then his role in "ruling out" found parachutes, could be suspect. Unsure. I believe the only place that info about the 28' canopy in a NB6 comes from, is Cossey's packing notes (since he packed both of Hayden's rigs around May 1971). Maybe Cossey mistakenly wrote down 28' instead of 26'? 377 has said a 28' wouldn't fit in a NB6 without closing flap modifications. The rig was bought at a surplus store, not from Cossey, so it's unlikely it would have a non-standard 28' canopy in it. The FBI memos do maintain that it's 28' canopy in a NB6. Hayden would have been unlikely to know canopy diameter. So I'm guessing only Cossey's packing notes gave the 28' info.
Yet another confusing detail.