Q20: Are slips with flaps prohibited in certain Cessnas?

A:   No.  Some Cessna 172's have a recommendation that extended slips with
     full flaps be _avoided_.  This is because the flaps on these aircraft
     are sufficiently effective to partially blanket the empennage during a
     full-flap slip, which may result in a gentle, but fully controllable,
     bobbing motion.  That bobbing motion has on more than one occasion
     unduly alarmed a pilot on short final, resulting in a less than
     satisfactory outcome.  Bottom line:  go up to altitude and try it
     yourself, with a CFI aboard if you prefer.  Then you won't need to worry
     about the recommendation.  [Disclaimer:  if the POH for your specific
     aircraft says something different, the POH takes precedence over this
     note.  Certain C-170s are reported to have such a prohibition, because
     they exhibit "exciting" descents in this configuration.]