RE: balancing a full flying stab
I don't know about all of the math that goes into calculating the balance point but I can tell you from my building and flying experience with planes that incorporate full flying stabs (which include a Tamjets F-18, two 1/8 f-16's, an F-100, and a Scorpion) that most manufacturers do not recommend fully balancing the stabs. Let them slightly fall down at the front of the stab when they are sitting in the fuselage and you will not have any issues. All of mine have been balanced in this manner and all work well. All of mine have the lead added at the leading edge of the stab at the root.
Gary