Now that I'm off for the weekend I can comment on a few things that you mentioned earlier. If you want to adjust your center and end points at an angle, to accommodate an angled steering assembly for instance, you can move them into the desired position while the joint editor is open. Select the translate tool. When you hover your cursor over the center or end point it will become a bullseye, indicating active for translation. If for some reason you don't get the bullseye cursor, which sometimes happens, close the joint editor and reopen it. This usually clears up this bug.

After you have your center and end points in position you can rotate them along the 3 axis' via the orientation fields in the joint editor. Here is a cube prop from left ortho camera with the center and end points translated and rotated 45°...