Sometimes you'll get a plane that is tail heavy. It might be too much glue, or it might have been made of an unusually heavy batch of wood. Most ARFs that I've helped people at the field with were tail heavy even when built properly. Do you think you may have used a bit too much epoxy on the tail? The general rule of thumb is 1 ounce to the tail, seven ounces to the nose.

I put a Thunder Tiger Pro .46 in my Easy Sport ARF and the CG came out perfect by moving the battery and reciever right behind the fuel tank.....go figure....