HP ratings are something you shouldn't go by, they can be manipulated just by changing the prop size and we never know what prop was being used to get the specs. A 1.20 is just a 20cc engine and a lot depends on the type, two stroke or 4 stroke. I have a big over weight Bipe I originally used an OS 1.20fs engine in and during tests using different engines the DLE 30 didn't pull it any better or worse then the glow engine. At the moment I'm setting the plane back up for flight but this time using a YS 1.20.
That's just this plane and a different plane will give you different results.