Why use 25 degrees (Cessna don't).
I'm with thing. It is vital to read the aircraft's manual and you must expect surprises. There are huge variations between different marques of the same aircraft. Some C172 models state a short field takeoff should be performed with 10˚ of flap and other models state flaps up. The C206 I used to fly performed considerably better with 20˚ on short fields than the 10˚ I was told I should should use. You'll never guess what the manual said...
The statement "
...that flap settings above 10-15 degrees created more drag than lift." suggests that you might not quit understand what flaps really do. Yes, as the flaps are lowered, the lift generally increases in percentage terms greater rate than drag, until a certain setting when drag will increase at a faster rate. But as long as lift is increasing, all things being equal you will be able to fly at a slower speed with increasing flap. But having maximum lift will not necessarily result in an improved short field performance. What you need is the optimum ratio between lift and drag for the job in hand. It is also important to consider obstacles in the climb out path. Getting off the ground is only one aspect of the take off. Also, an engine failure on departure with the maximum possible flap selected might mean the aircraft becomes un-flyable by a normal pilot.
So returning to where we started, an aircraft's operating manual describes how it should be flown. Not a chap in the bar or an idiot like me on the internet.
PM