Okay I always have a hard time explaining this but here we go. To me the easiest way to do this is from the bottom up. If you know how much travel you are getting than we can start from there. Example: 3" of travel on a 4" air gap, you need to set the top of the cup (25-9090-70-7) at the end of the travel. On the 25-9090-70-5 you need to be .300 down from end of cup or at groove that we cut in bump cup. This will get you into max travel at 1.5 to 1.6" into the bump. If we need to shim bump up to make load we have shims to do the with in .060 and .125" thk. We also have a 1.0" spacer and a .300" thick spacer to move bump cup up.
To help understand this a little better here is what some of these terms mean.
Bottom of bump: This is the bump at full compressed, this would be the end of the shock compressed to the line that says "Bottom of Bump". This will have the bump at full compressed and at max load for the tire. This is at 1.600" into the bump.
Air gap: This is the space between the bump and the end of the body where you can see the shaft showing.