As you have already seen, lots of people seem to remember private
interpretations or letters from the FAA ruling one way or another.

The regulations say that you have to be rated in category and class to act
as safety pilot. That means a pilot certified for airplane single engine
land can act as safety pilot in any single engine land airplane, from a
Pilatus PC-12 to a Cessna 152. The appropriate FAR says:

(b) No person may operate a civil aircraft in simulated instrument flight
unless --

(1) The other control seat is occupied by a safety pilot who possesses at
least a private pilot certificate with category and class ratings
appropriate to the aircraft being flown.



There is no regulatory requirement that you be able to act as PIC in order
to log PIC under any circumstances. In fact the FARs are quite clear about
when you may log PIC:


(e) Logging pilot-in-command flight time. (1) A recreational, private, or
commercial pilot may log pilot-in- command time only for that flight time
during which that person --

(i) Is the sole manipulator of the controls of an aircraft for which the
pilot is rated;

(ii) Is the sole occupant of the aircraft; or

(iii) Except for a recreational pilot, is acting as pilot in command of an
aircraft on which more than one pilot is required under the type
certification of the aircraft or the regulations under which the flight is
conducted.



A strict reading of these two regulations would indicate that a private
pilot holding a certificated for single engine land airplanes may log PIC
for the time he is acting as safety pilot in a complex or high performance
airplane whether he is signed off for those airplanes or not. Others in the
FAA or anywhere else may differ in their personal opinions and may even have
written letters or articles stating their opinions, but those letters and
articles are just that: opinions. It should be remembered that many of these
people are attempting to enforce their opinion when they could not get their
ideas enacted in the regulations. They lost in committee and review, so now
they are attempting to mold public behavior through threats and
intimidation.

If the regulations do not mean what they say, then the regulations need to
be amended. Until then, the regulations have the force of law.

All of that being the case, my own personal opinion is that any pilot would
be very foolish to attempt to act as safety pilot in any airplane that he
was not fully qualified to operate. I think the regulations should be
changed. But right now the regulations are specific: you may act as safety
pilot and log PIC while doing it. There are no loopholes, gray areas, or
private interpretations here that make a convincing argument that the
regulations do not permit it.