This is something I posted in my build thread a while back. It's just my view on it so maybe it'll help clear up the muddy water a bit. I couldn't be happier with how my suspension performs so I think my view was pretty accurate.
Here's the quick and dirty on my view of squat and anti-squat, just to help explain what the adjustment in the upper mounts actually does:
Antisquat tells you if a car is going to squat or rise when accelerating. Now go back to physics class and apply what you learned--for any action, there is an equal and opposite reaction. When the rear end of a car squats for that first split second when launching (action), the rear tires lose traction (reaction). Conversely, when the rear end of a car raises during acceleration (action), the tires push down onto the pavement....or rocks, or whatever surface you want to talk about(reaction). So, it may appear that high AS is a good thing, but here's why it's not--and it's the exact reason I want to reduce my AS--after that instant downward force on the tire, the weight transfer is over and the tire loses traction. This continues to happen if you're on a loose surface and results in hopping (or rock humping as we call it). The higher the AS, the more severe the hopping.
The percentage of anti-squat is determined by the location of the instant center. This point is determined by the imaginary lines drawn through the middle of the suspension links--where they intersect (from a side view) is the instant center. The percentage of anti-squat refers to the amount of weight taken through the suspension links. For example, 80% AS refers to 80% of the weight transfer being taken through the links and the remaining 20% is taken through the springs, resulting in downward squat. 100% antisquat is a 'perfect' situation in which the links take all of the weight transfer and the springs take none, resulting in no squat OR rise of the rear end. In this situation, the instant center falls on a line that passes through the rear tire contact patch (100% AS line) + the intersection of two other lines--a flat line through the CoG and a vertical line through the front tire contact patch. Lastly, +100 AS (110% for example) induces the rear end to actually raise when accelerating. It sounds crazy technical but if you draw it out or download the pirate 4bar calc, it makes perfect sense. That is what I'm trying to achieve but it's difficult since the exact location of the CoG isn't perfectly known. Instead, you can only make a close prediction and I used the throwout bearing, which is approx. 25" above the ground on my rig. That's why there's adjustment built into the upper link mounts--as you should now be able to see, raising or lowering the frame end of the upper link changes the angle, resulting in a higher or lower instant center.
A couple other things--the CoG is a very important location. The weight transfer occurs/pivots around that point. So, if the IC is behind the "100% AS line", the rear end will raise. If the IC is in front of the 100% AS line, the rear will squat. Again, if it falls on the line, the rear will be neutral, the ideal situation. I'm going to do my best to keep the AS just a few points under 100% since my shocks counter squat (Bilsteins). Hopefully this helps clarify the muddy subject of suspension geometry--after reading a lot and messing with the suspension calculator, things became very clear. There's literally a ton on the subject out there and really, once you apply basic fundamentals to the case, it all just makes sense.
FYI, that should explain why I never recommend RC and BDS's long arm kits. The rear upper and lower mounts @ the frame meet at a single point--ie, no vertical separation. So, the IC is far back and low, giving you a ton of AS.
Help at all? You need to download the calculator to get a visual. Plot your current suspension on there, study up on link suspension some more, and you should start to get it. Once you do, it'll all click and you'll say, "ooooohhhh, now I get it." Don't shoot for 100%. Shoot for 60-90% AS. You want that small bit of squat. On one very tough wall, I compared the previous setup with a ton of AS vs. my current setup, which should be around 8-90%. I feel much more comfortable hitting the gas hard on this super sketch, steep wall. The front end will always feel light unless you have a suck down winch but the more you do it, the better you'll get to know your rig and you'll "feel it." You'll go from being scared any time you feel the front end lighten up to knowing that you're OK. It takes a while and it takes some ***-clinching but eventually, you'll start to feel more comfortable.