Almost all low compression motors will lose power by using high octane fuel. This has been proven time and time again on the dyno.
http://www.rc51.org/fuel.htm
I read the link. The information in this link was testing on four strokes and mostly low compression street bike engines that were designed to run on pump gas
I agree that if your engine does not need high octane fuel....do not use it.
I have made about 200,000 dyno runs in my 40 year career working on four and two stroke engines. My dyno test results on four strokes agrees with the link provided but test result on two strokes does not agree with the above link when it comes to testing fuels on two strokes.
Any large displacement single cylinder engine especially 500 cc two strokes, will have or is on the verge of having detonation problems regardless of the compression ratio, at partial throttle and higher RPMs due to the scavenging problems that is inherent in all two strokes. The four strokes scavenging process is totally different than what occurs in a two stroke. Detonation is directly related to cylinder pressure, mixture temperature, mixture purity, and the distribution of the fuel within the combustion chamber during the combustion process.
Putting high octane fuel in a low compression ratio two stroke engine will usually lower the power if the ignition timing, the exhaust system and the jetting is not optimized for the fuel being used.
The design and operating principles of Two strokes and four strokes are so different, one has to be very careful using testing result from one type of engine design to try to sell ideas or products that do not share similar principles or apply to engines that operate on completely different principles.