Yes pull pull rudder makes a big difference in CG and I would do it if I were you. 4 ounces in the tail equates to 12+ ounces in the nose. So you can save yourself adding close to a pound of lead if you just install a pull pull rudder. Then you can move your batt's up front if necessary. My guess is that with the pull pull rudder your CG will be right where you want it. Mechanically a push pull is simpler and does not have the slack issues of a pull pull rudder that is anything but perfectly installed. But the little amount of slack on one side at full deflection is usually no big deal. The pull pull is also lighter since it doesn't require a 2+ ounce 36 long servo extension. It's usually very close to the receiver. Another great way to push the CG forward is to use a very light tail wheel or entire tail wheel assembly. There are foam wheels out there that will save you a half ounce to an ounce. The RC Blimp production tail wheel assemblies with titanium and CF are the lightest and best out there.