Some brush overlap can indeed be a good thing, that is it can increase output power... too much overlap just tends to use more input power then you gain in output power and amp input goes up while effciency goes down. I personaly belelive there is little or no reason to ever have brush width greater then about .175", which is what you wind up with when you trim a laydown brush by .015". A really high RPM motor will typicaly bennifit more from a slightly narrowed laydown brush then will a moderate RPM motor will...
Interestingly enough, a D5 motor has brushes that are about .175" right out of the box. However most Mod guys won't even use them that wide, they typicaly narrow them to about .150 which is the width of a standard stand up brush....
Since I didn't dyno the D5 Mod motors in those graphs, I have no idea if the brushes were trimed or not. My assumption would be that the brushes were full sized P-94 brushes, simply because there was no notation that the brushes had been altered.
So... the brushes on all the motors in those graphs, may very well be juat about the same width.