The Frise discussion is interesting, but doesn't appear applicable to the C-172. The 172 ailerons are of the "differential" type. See the rigging specs for the ailerons in the service manual or TCDS.
See
TCDS 3A12. (C-172) For a C-172M (early '70s) model, the specified aileron displacement is 20 degrees up and 15 degrees down. It's bit difficult to explain in words how the amount of differential is controlled, but suffice it to say that when the bellcrank that connects the aileron control rod to the direct and and crossover cables is positioned correctly, the amount of differential travel will be correct if the rigging instructions are adhered to.
As is the case with Frise type ailerons, the differential travel is intended to reduce the amount of adverse yaw induced by aileron deflection. At higher AOA there is just enough adverse yaw to remind one of the need for rudder for proper coordination. I personally find either of these designs preferable to an aileron/rudder interconnect bungee. Especially when landing in a crosswind!
And yes, the "piano-hinge" at the upper surface is a relatively simple and inexpensive method of attachment which seems to work good and last a long time, even if they do require some mx attention. They used it on the elevator trim tabs too. The angled forward surface of the aileron is what allows downward deflection of the surface. Interesting that Cessna decided to go with an elegant single slotted Fowler flap on the 172 rather than a simpler and cheaper plain flap design isn't it?
Anyone ever hit their forehead in the trailing edge of the aileron and imprint themselves with a bloody diamond? If so, you are automatically eligible to be a member of the Cessna-head dummkopf club. I've been a member for over 30 years...
Long live the mighty Skyhawk!