Our agreement as safety pilot was that I would be the eyes outside the
aircraft to see and avoid other aircraft (such as the B727 that took off from
SFB and
crossed ahead of our path.).
It is the see and avoid that I believe makes me responsible for the over all
flight path.


Nope. Your agreement was you were the eyes outside the aircraft. This does
not make you the "final authority as to the operation of the aircraft". You
are a sensor, not a processor. The other pilot is still responsible for
responding to your input in an appropriate manner. Even if you are compelled
to grab the yoke to prevent an inadvertant customization of the aircraft (which
would fall under the responsiblity as safety pilot), you are still not PIC.

Not by the agreement you describe above.

Jose



--
(for Email, make the obvious changes in my address)