So I took a deep breathe and did a little more digging. I looked back at historic reviews, circa 2012 for this unit, and the power increase on MMR's dyno was minimal. Nothing close to a 15% power increase. However, the spool time on an unloaded motor was measurably faster due to the slightly modified timing and smaller diameter of the flywheel, which made for a snappier throttle response. This was on a 29.5cc Trevor Simpson motor.
I can see running a smaller diameter flywheel with the same overall weight of the stock flywheel making throttle response snappier. It makes sense. The same weight on a shorter flywheel will not produce the same strain on the crank at the end of each stroke and absolutely should increase throttle response. This would also explain the need for more aggressive cooling. You have a smaller surface area trying to move the same amount of air to cool the engine.
I think with the "butt dyno", this piece of kit will probably feel like it makes a more powerful motor, but the reality is that it just makes the same power, but it a bit more responsive to throttle inputs, which I don't doubt. I still feel like it would only make a difference to someone on a competitive circuit where the extra throttle response would give them that tiny little edge.
But hey, if you have the money to burn, go for poop and let us know if it makes your model any faster! BTW, vids, or it didn't happen!

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I'm looking forward to hear from Sean @ OBR on this. He definitely has my ass beat as far as insight on these little 2-stroke bastards!