from what I understang if you add a slider (cheater line) to your line in the water, that would count as your 2nd line. Don't try 2 rods 4 lines, that is a no no! unless you are in maine.
its illegal in nh and you could get in trouble even if you use one rod with two lures. i remember they were changing the written rules so that you could not branch out a line into two lines but i dont know if it made the book. im sure the game warden will interpret it as illegal. in maine its legal and pretty common to run a slider rig even with two lines in the water. the way nh was looking at writting the new law wouldnt let you branch off on a cast of flies which is pretty common the world over. dont do it in nh, it is cheating