Amgle isn't really a good indicator of what it will want. The centerline of the front heim from the ground is a better indicator. This measurement along with the rear axle centerline from the ground is what matters. Think about the imaginary line drawn between those two points. You could concievably use many different mounting posistions to attach the ladder bar to the rear housing. The bar could end up point up/ down, or level. If those two points remain the same, nothing changes. Most brackets mount in a similar spot on the housing, but not all. This is why people use the bar "level or slightly down" idea. Not because thats necesarrilly where it needs to be. But it happens to fit for their cars set-up. The suspension would react exactly the same. Now what can we change? The height of the axle C/L based on rear tire diameter. The length of the ladder bar itself. This is chosen when they are built. Generally somewhere between 28"-36". And lastly the C/L of the front of the bar from the ground. This will have an adjustable range. How do we chose? Expected power, weight distribution, and type of tire are the four that I think make the most difference. Radial tires will want the heim C/L high. Bias slicks lower. High power will want a longer and lower C/L. If the car doesn't have a ton of power and it's heavily weight biased towards the front the bar could be shorter. No prep needs a higher C/L. 28" is very short. The average bar is about 32". A shorter bar acts on the anti-squat line similar to a higher heim C/L. Ladder bars can provide a ton of hit. Thats why sometimes you can't get the C/L low enough. It takes a longer bar to get the C/L down on the anti-squat line. Radials and no prep want a higher C/L. My car runs 31.5" bias slicks with tubes. The bar is about 7.5" off the ground. The bars are 36" long. Car has 55% of the weight on the nose. Even with 13.5psi and the shocks tight on rear rebound. It wads the tires 20-25 out from the start. Think about how hard a shorter bar would hit.
Doug