I have an expression that I have used for many years: Go by the book, and when the book doesn't work, throw the book away and do what works.

The bottom line is If the plane flies like it is tail heavy, then it is probably tail heavy - regardless of what the book says.

There is also NO SIN in adding weight. Sure, avoid it if you can, and some guys will say "Use a bigger battery instead of adding dead weight" but the fact of the matter is, you HAVE a battery, why spend 50 bucks for a new one when 3 cents worth of lead will accomplish the same thing?