like said above to many variables. My knowledge is if your making a square tube run the big tube on the top at 12 and the bottom at fifteen works for just about any rig any lift any travel. With that said since you have duals it should be 7 inches further back then stock so make the top piece 19 and the bottom 22 and it should work but measure before cutting I wouldnt want you to cut it out and have it stuff up into your t case.
