yo i got mine balanced perfectly at 4 inches now.

First, i took the fuel tank out. I then cut the cross member on the plywood below where the fuel tank sits. I then put the battery there and then the fuel tank with extra foam rubber to protect from vibration. That way works awesome and it doesnt take that much work.

When i was taxiing it in my yard, the thing seemed really quick with just the .40, i think itll be fine.