The choice of flaps for 100 series Cessnas will forever remain a personal preference, and be correct as long as the flight is safe, and the Flight Manual procedures are adhered to. Agreeing to disagree is fine, but for every pilot who tells me that they use different flaps settings for different conditions, I will tell I land every aircraft I fly, with full landing flaps for every landing, and the greatest permitted flap setting for takeoff.
My objective is to achieve the slowest speeds practical, which will result in safety, and the least wear and tear on the plane. Yes, with a 7000 foot runway, and a jet behind me, I will fly up to the intended touchdown point, then deploy full flaps for the same slow landing. It works out just the same.
If doing every landing with full flaps is considered dangerous by some, I would examine the skill of the pilot involved. The oft used reference to the "test pilot in the brand new plane" getting better results, is a myth. The procedures are the same now, as they were 40 years ago, for obtaining performance data, and super skill is not tolerated during flight tests for certification. If the aircraft will not achieve the performance in the approved flight manual at any age, it probably has a defect, and should be repaired.
For certified aircraft, you can depend upon the rudder to be as effective as you need it to be, with any flap position. This relates to crosswind landing capability. Certified aircraft are required to demonstrate crosswind landings as follows:
Directional stability and control.
(a) There may be no uncontrollable ground or water looping tendency in 90 degree cross winds, up to a wind velocity of 0.2 VS0, at any speed at which the airplane may be expected to be operated on the ground or water.
(b) A landplane must be satisfactorily controllable, without exceptional piloting skill or alertness, in power-off landings at normal landing speed, without using brakes or engine power to maintain a straight path.
(c) The airplane must have adequate directional control during taxiing.
This is something I often have to test for, and you'd be amazed just how much control is available.
I agree that the 172RG Flight Manual does specify zero flap for takeoff, so that is what the pilot should do. I find it unusual though, as all of the 182 Flight Manuals I have specify up to 20 flap for takeoff, and the wing and power loading of both aircraft are quite similar, with I believe the same airfoil.
Fly what the Flight Manual says, but consider the wear and tear on the aircraft too...