My experience has been great in my 525 which are basically the same 48 minus the external preload adjuster. I think Pete147 or something actually has it in his 950.
Best advice is to call them. The guy I spoke with was very helpful, a bit opinionated , and it all worked out great.
The shim stack in the compression circuit is what you are changing, by varying the amount, size and thickness of the shims, you are changing the valving, which has nothing to do with ride height etc.
It all depends on what type of riding you are doing. I was brutally honest with him about my skill level and the terrain I was riding in, he helped me pick out the correct shim stack, and possible alternatives if I wanted to soften it up or vice versa. So far it has been great, and honestly I am not a good enough rider to be able to tell the subtle differences anyways.
The bright red thing replaces your stock compression valve body. The compression circuit (basically the entire thing you see attached to the valve) unscrews from the bottom of the fork under the rubber cover.
Directly to the right of the Ultra Valve are the shims, hard to see, they are really effin thin. I couldn't believe that's all it is, but there you go. I forget how many came in mine stock, but I probably revalved with 50% fewer shims. Maybe 10-11 total? Forget anyways it's in the instruction.
The large rod with the thick spring is your rebound circuit, which I also revalved with a kit from Moto Pro as he recommended it for woods riding. You can see the shims just to the left of the nut (which needs some grinding to come off ) This rod then goes into the aluminum tube you see. The compression valve gets threaded into the bottom.
I borrowed some photos that were helpful to me from KTMTalk.com which is a fabulous resource for into on this suspension. I hope they don't mind.
Next, is a photo of the Base Valve / Compression Holder: