It seems to me that you have two issues, balancing, and the total weight. If you remove the lead and weigh the airplane and it comes out above the recommended weight then so be it. It is what it is. Unless you are a highly competitive pattern flyer I would not worry about it. As far a moving the tank, as I said the tank fits right behind the second bulkhead without any cutting again see my pics. Finally I noticed when balancing mine that the mark has to be right on, if you are 1mm either way it will fall to the nose or the tail.