The thin "running line" should be 2-6 feet outside the tip with the thicker head outside. Most shooting heads are about 30 feet, so 32-36' total (plus leader) is about what you should have outside the tip. If you want something that might help a bit to get you started you can put a dash with permanent marker on the running line comes off the reel with the head and a couple feet of running line outside the tip, but you should be able to tell with your eyes closed after a little practice just by the feel of the line and loading on the rod.
If you try to false cast with more line out (say 30' of head and 10' of running line) the loops will start to collapse because of the thinner running line. The idea is to get good line speed with the heavier head and then "shoot" the running line on the actual cast.
Having just a little bit of running line out of the tip shouldn't collapse the loops, and it will also take potential stress off the junction between the shooting head and running line when you release it for the actual cast (rather than being inside the tip top, where it might snag on the tip or a guide under a lot of pressure).
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