Build a box in the nose to hold the battery and the lead. There is room for lead where the nosegear used to be. Boxes can be heavy wood. After all.............

Weigh the nosegear you left off and you'll get an idea where some of the imbalance came from. Figure how much the tail gear weighs and multiply that by say 2.5 and there's some more weight to consider. That won't change anything, but that plus an 8oz lighter engine/muffler ought to give you an idea if the model really is abnormally tail heavy.

About time to fly it??? Tell us how it goes.