I don't know about you but your airplane sounds fairly well-balanced. Adding 100 gms to the tail is extremely unusual, but what matters most is whether your balance point is correct. When a plane is tail heavy it is very hard to control in pitch because it exaggerates every input. It's climbing so you give it some down and it dives so you give it some up and it swoops up again, without being able to get a happy medium. That's tail heavy. It will make your knees shake at the least. Simply climbing by itself does not mean the plane is tail heavy. If you can trim out the climb, then the balance point is not bad.

However, when a plane feels a little uncomfortable, even after trimming it out, it is often because the balance point is close to the point where it goes unstable. Moving the balance point forward, often even just a little, can smooth out the flying. You said it might have been a little tail heavy when you balanced it, so a good first step it to move the balance point forward so that you are sure it is not behind the point given on the plans.

If you had to add 100 gms to the tail to get to the balance point on the plans, first double check to be sure you really have it right. Then, if so, see if you can move the battery pack to improve the balance, instead of adding dead weight.