If you could take 1 oz from the tail end, it would be about like adding 4-5 oz to the nose depending on moment arms.
If it has a solid sheet tail, I might change to a built up one.
If you try the lead spinner idea, you would have to hold the spinner solidly, somehow keeping in mind it is going to get very hot. Also the back edge of the spinner would have to be exactly level for close balance. don't over heat the lead or you would melt the spinner. Then what happens if it comes loose ? I wouldn't try it.
Maybe a bigger motor?