This goes along with so many other measure twice cut once adventures. When building aircraft cable assemblies the best way to get a good swage length is to start from the end and work back. You need to figure out where to cut the cable. Then you can leave the same size tail on each swage and all of your cables will land at the same height or very very close. If you try to work out where to measure to on a thimble or in the middle of a swage it never quite works out correctly.
Here is my method for working through getting a correct height to swage at. First build the whole assembly but do not swage. Then get a tape measure next to all of it. Measure from what is important and easy to get the tape to attach to. When doing pipe the top is usually what you can work from. Then grab the tape and the cable assembly and take it apart. It is important not to let the parts slip at this point. Once it all comes apart you can then see where the tail lands in relation to the pipe or whatever you are supporting. This will tell you the offset for the assembly you are using. Since most jobs are different this is worth doing with the actual parts and not just re-using the last jobs measurements.
Once you get the hang of it there is very little measuring involved. It should be a pretty simple process. Don't overcomplicate it with a lot of trying to figure things along the way.