Oh, and to answer the question about whether or not seeing your downrigger ball in the FF affects what you see below, the answer is: yes, it probably does. However, remember that the sonar's signal is an inverted cone which gets wider and wider the deeper you go. The downrigger ball is something like 3-4" in diameter and so represents only a tiny part of the return signal.
Take a look at this picture from my sonar in which I had two downriggers out (these are the horizontal lines):
as you can see, there were plenty of fish below the downrigger ball that were still identified. You may also want to check out Lowrance's sonar tutorial:
http://www.lowrance.com/Tutorials/Sonar/sonar_tutorial_01.asp
as it offers some good information.
Hope this helps.