The thing is you just moved the weak spot to the end of the pipe sleeve. We use steel handles on sledge hammers on commercial boats. Good for x number of hits until metal fatigue sets in. The only thing that ever worked was to weld in a solid plug about 18" long, then pipe over that, with about 4 plug welds. Moved the weak spot far enough away from the head that the leverage length of the handle was no longer an issue. In the case of a monster maul, the weight of a long plug becomes an issue, since the stupid things are already too heavy. Hence it becomes a maintenance issue. Repair as needed. Without doubt though, a sharper maul will not stress the handle as much.
