I have quite a few Coyote Stock customers. They run at 3000lbs, use a 5.0L 435hp rated factory sealed crate engine, must use a single 10 or 10.5" disc and a diaphragm style pressure plate, spec transmissions/ratios, and must use the clutch to shift. Here's some recent slip data from a run...

1.296
3.868
6.059
110.11
7.968
9.610
134.94

When everybody's making the same power, it can be especially sweet when you get the clutch tune just right. When the clutch hits too hard, it either pulls the engine down too far or knocks the tires loose. Hitting too soft is also counter productive, but there's a sweet spot in between where things work amazingly well. Basically you want to match the clutch's clamp to the engine's power, as this can effectively raise the engine's average rpm, which in turn allows the engine to produce more power in a tighter time frame.

Here's a simplified example to help explain why you want to keep average rpm as high as practically possible-

Lets say a car has the power to gain speed at an average rate of 6000 rpm per second in 1st gear. Let's also have the clutch slip until .5 sec into the run with the tires remaining dead hooked. If the car launches at 6k and the tires are stuck, the clutch will pull engine rpm down to 3k by the .5 sec mark. Then from .5 to 1.0 seconds rpm will climb from 3k back up to 6k, as the engine regains the lost rpm. What all this boils down to is that during the initial 1 second after launch, the engine's average rpm was 4500 rpm, which means the engine made 75 revolutions over that 1st second of the run.
...Now suppose that same car launches at 6k, but now the clutch slips just enough that the engine does not lose any rpm over that same 1 sec period. Now the engine's average rpm was 6000, which means it made 100 revolutions during that initial 1 second period.
...Here's the thing- both left from the same rpm, but the launch that didn't lose any rpm actually packs 33% more revolutions of WOT power production into the same 1 second time period. If the clutch also slips just right after the shifts, you can pick up some power production there as well.

When you understand what you need to do, you can likely make things come together on your own. Here's a few things you can do to an overly aggressive clutch to tweak it closer to that sweet spot...
1- less aggressive friction material
2- smaller diameter disc
3- reduce effective diameter of the disc (trim away some of the friction material's face without reducing overall diameter)
4- reduce clamp pressure either by swapping to a weaker PP/spring, different fulcrum or shimming your existing PP away from the flywheel
5- temporarily hold back some clamp pressure with your foot, basically ride the clutch out for 5-10 feet. Adding an adjustable spring loaded pedal stop can make it easier to consistently find the sweet spot in the pedal travel
6- temporarily hold back some clamp pressure with a timed mechanical device (this is what my device does)

Just putting this out there to show you don't necessarily have to have an "adjustable" clutch to be quick.