Apache-

With the black shoes you cannot get much higher engagement point then 6000RPM when the set screws are turned in 1.5 turns. That is what I measured with the rpm device in the past. After shortly warming up it even lowers down a bit the start of engagement point.
This is due to the top surface getting warm and more grippy from the black shoes.

The black ones are great for dusty slippery conditions or in wet but I find the new white ones running better as they keep engaging more stable from the start.
They do not suffer this getting more grippy effect.
I drilled out the black ones in the past which makes them lighter as well to raise the RPM level if that is what you are looking for. That is something you can do easily yourself.
But be sure you do it symmetric on at least each opposite shoe.
As otherwise you get a weight differance on your crank shaft putting unnescesarry extra forces to the bearings ones it rotates.
Taking out some material makes a considerable raise in RPM level on the black shoes if that is what you are looking for.
If it is to much the raise in RPM and you cannot lower enough by releasing the set screw, you can always screw in a set screw in the hole you drilled which adds weight and then lowers back the RPM engagement point.
a 4.5mm hole is good as you can use a 5mm setscrew for putting back in if you like.
This is what I drilled in the past, 2 holes per shoe.