Of the dozens of messages regarding the flight properties of a Legacy with
unlocked canopy, there are only two pilot reports. Assume for a moment that
the two pilots who were actually there are accurately reporting their
experiences.
Further assume that all the armchair quarterbacks were not there and did
not experience the flight characteristics of a Legacy with open canopy.

One pilot says the airplane was stable, but windy and noisy.
Another pilot said his aircraft had significant pitch oscillations.

What would make one aircraft pitch stable and another very
similar aircraft statically pitch stable, but dynamically unstable?

The simplest explanation would be a CG difference, though it could also
be a different flap position, gross weight, or maybe prop size and pitch.
If the aircraft is flying near its aft CG limit, and the open canopy shifts
fuselage lift forwards, then a dynamically instability (oscillation) might
result. At higher angle of attack, the effect of fuselage shape might be
more pronounced, leading to the observation that the oscillation was
worse at lower speeds.

Two (or more?) other pilots are believed to have had open canopies
and not survived. I'm inclined to believe that the reports of oscillations
are accurate and could have been worse.

BTW, an unlatched parallelogram canopy in a 235 opens about 2-3 inches and
makes lots of noise as soon as the prop blast hits it. In flight, one
improperly
seated latch makes a loud bang when it lets go, but can be resealed in flight.
Two or more latches open would be annoying at the least.

-bob mackey