I really like the look of the mallet. I might make the handle thinner, when I do it though. The weights inside the hammer are suppose to move a bit. It helps with the hammer’s blow. If you think the movement will bother you, you could put some linseed oil in there to make it smoother. They put oil in some commercially sold mallets.
I made a clamp like he did to clamp things through dogholes. I however didn’t remove the top part. Instead I just removed the bottom rivet. It works fine and it is less tricky than removing the top part.