For the stock engine the 10 teeth pinion is just fine, no magic in stepping down unless you get an engine with higher ideal rpm operating area.

Superhornet: Swisscheasing your heli mgiht give that extra 4% of performance if done exactly right, but other drawbacks follow, the rotor actually needs some weight for stabile operation,, preferably weight would be added to the rotor assembly of these micros if there was enough power for it,, would give it more momentum and less sensitive to every breath in the room. Secondly drilling all these holes doesnt do any good for blades and other parts keeping their intended shape when exposed to the forces of fligh, they will flex and deform much more wich is something one really should try to prevent.