A C150 isn't much of an airplane. We used to joke that we used ours
for taxi trainers. On hot days at our 3000' airport elevation there
were times that they wouldn't climb past 4000' when at gross. They're
a draggy design; the earlier straightbacked models were lighter,
faster and probably climbed better, too.
If you look at the 150's wing and then at a Super Cub's or some
other STOL airplane's you will see a big difference in camber and
leading edge treatment, both of which have a lot to do with low-speed
performance. I once flew a Super Cub that had vortex generators
installed on the wing, and it would approach at 30 knots. You'd never
get a 150 anywhere near numbers like that, even if you got slats to
work. The whole airplane needs to be purpose-designed, and the 150 was
designed to be a simple, strong, cheap airplane for training pilots,
not for flying into tiny unimproved strips.
I also have a few hours in a 90-hp Alon Aircoupe, the last
iteration of the venerable Ercoupe. It had factory rudder pedals in it
and a slide-back canopy, but the rest of the airplane was pretty much
the old design. It grossed 150 lbs less that the C150. Those 90 horses
outpulled the O-200's 100 hp by a wide margin; the airplane took off
shorter, climbed much better and cruised 20 mph faster than the 150.
It led me to believe that the O-200 is a bit over-rated, or that the
150 is a lousy design, or both. At any rate, we no longer run 150s in
our school.

Dan