In a C172 you wouldn't want to use more than 20 deg flaps for the purpose of slowing down and minimizing turn radius. You get little more lift but a LOT more drag after that.
And, as we see in the example above, using flaps in a GA airplane does not work as well as using more G at Vx or Vy clean.

Minimum turn radius
 

Dont forget about the effect of wind. If say you have strong wind from the right, it is best to make your turn to the right. Turn to the left and you will make a much larger radius turn. There is a discussion on this in the latest US AOPA magazine in connection with the fatal accident of Lidel in the East River in New York when the wind was from the east and possibly caused the aircraft to end up in Manhattan.:=

For a constant-speed, constant G turn, the end point for a 360 will be the same. However, turning upwind will help for 180s.

Be careful, though... An initial turn upwind will result in a turn that is NOT of constant radius over the ground, and may be viewed as "decreasing performance" when turning downwind again (e.g., after 90 deg of turn if it started as a direct crosswind). The significant change in ground track and its effects on visual perception is the REAL cause of the dreaded "crosswind turn stall"...

This whole subject is handled really well in "piloting for maximum performance" by Lewis Bjork.

There is a really interesting story re: a dead-end canyon flight and using all the tricks to tighten up the turn to as unfeasibly tight an angle as possible and still stay flying.

I learned a lot of other stuff from that book too - well worth a read, and far better written than many,
SB