[Kromm]

The main reason to improve Power Blow is so that it will work more quickly. Yes, there's also a magic number where it allows more ST, but Power Blow is raised first and foremost to allow one to work faster. As the primary application of the skill, I would not allow a technique to speed this up.

If you want a faster, cheaper combat ST bonus that works much the same way, then buy something like this: Striking ST (Chi, -10%; Costs Fatigue, 1 FP, -5%; Requires Will Roll, -5%; Takes Extra Time 1, -10%) [3.5/level].