This is no miracle engine, it has a very ordinary bore/stroke ratio. When you over prop an engine you end up with much less power and a needle range that becomes overly critical and much more difficult to adjust to a good setting that it will hold.

Airplanes fly on power, the top speed is directly proportional to the cube root of the available power. Matching the prop load to the engine's horsepower curve is how you achieve this. Since this engine makes it maximum power at 16,000, you would want to prop it to turn in the 12K range, with the knowledge that it will unload one to two thousand in the air in level flight. It will unload a bit more when in a dive, so a 12k ground rpm keeps you well below the maximum rpm.

The 55 will be much happier and easier to operate with a 12-6 or 12-5 with your trainers.

As far as OS and their recommendation - it's either to hold down noise for some markets that they serve or pure marketing hype.

As far as tips on running, this is a easy to operate, smooth running engine with a great idle and transition.