Jim Macklin wrote

(5) Model 172L (1972 model)
"This airplane must be operated in compliance with the
operating limitations as stated in the form of placards,
markings, and manuals:

Yeah Jim, and we all MUST comply with all highway speed limits,
even when they were 55 mph. Hell...my speedometer even had a
big red mark at 55 mph.

A lot of those placards, markings, and manual limits are just
because the manufacturer did not want to spend the time and
money in order to seek certification for a particular item.

Such is the case of the "no slips with flaps" contained in the
manual for a lot of the C-172s.

Bob Moore