Its really easy on a big twin if you break it down.
1) The cable adjuster adjusts the cable
2) The set screw adjust the push rod
3) The ball ramp and release bearing sit between them. The ball ramp needs to be seated to get a good adjustment. And this is where the Harley way of doing it sucks. They have you back the cable off so far that you cant feel the ball ramps.
So just back the cable off a turn or so.
Then jiggle the lever as you turn in on the set screw. If you run out of lever free play, back it off another turn and repeat. You can actually feel the balls seat as you turn the screw in while jiggling the lever. When the set screw seats, you will have zero lash on the push rod and the balls will be seated at the base of the ramp.
Then back the set screw off 1/2 a turn on used plates, or 3/4 to a full turn on new plates, and lock it down.
After that set the cable adjuster till the slack is gone, then back it off until there is about 1/16th slack at the lever.
Now measure how much lift you get at the pressure plate. About 50-60 thousandths is what you are looking for. And it should be seated at .000 before the lever is fully released.
And to be sure, new disks will want another adjustment in a 100 miles or so.
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Now about those little spring disks, seats, and big thick Belleville springs.
That little concaved spring at the bottom of the clutch pack is what gives you a friction zone. And the little flat ring it sits on determines where the friction zone is in relation to lever pull. So when you take them out to install an extra plate kit, you just removed the friction zone and the ability to adjust were the clutch engages. That's automatic transmissions 101. And if you weren't aware of it, the Harley clutch is just an adaption of a clutch out of a GM auto trans.
And when you add that big SE Belleville spring, you actually give up some of your pressure plate lift. The big spring causes the right cover and clutch basket to both flex when you pull the lever. And on some set ups, the thickness of the spring comes into play. This limits how much pressure plate lift you get. And some times brand new extra plate kits with big springs drag badly when adjusted by the book. Basically to the point of breaking stuff. In general, they need the set screw backed out less than with oem plates. But you have to make sure that there is still some free play on that adjustment. One of the old school tricks was to break the disks in with a light spring, then swap it out for the heavy spring after the plates had heat cycled (burnished) a few times.
Now with all of that said, big springs are to be avoided on street scooters. If you add more clutch surface, you can run a lighter spring. That was one of the things that made the old RP Pro Clutch so popular. It would hold a lot of power, with a fairly light spring, because the plates were massive. But big fuking springs on top of extra plate kits are a lot less money than swapping out the hub for one that will take bigger plates, so that what you see in scooters out on the street.
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