In my opinion 20oz (1 1/4) pounds is a lot of weight if you are talking about a 5 to 6lb aircraft.

I am wondering, is there anything you can do to lighten the tail. Is there excessively heavy hardware that has been added? Have the elevator or rudder servos been put in the tail? If 20 oz has to be added to the nose then maybe only 4 or so needs removed from the tail.

I would also like to add in case there are any new comers reading this. Yes, balancing is typically done with an empty tank. But an airplane should still balance properly once the fuel tank is full.

Good luck