The easiest way that I have found is:
Cut the upper (or lower if you choose) blank to size with the center band piece included.
After drilling, square the center end of the blank (I use a jig with a disc sander)
Drill the piece of wood or other material for the center band.
Sand one side flat.
Glue the blank and the center band to the brass tube and to each other. (I use polyurethane glue)
Clamp.
This takes longer to describe than to do. I use the same method for bands at the upper end of the pens. Some can be seen on my website.
I have used wood, corian, acrylic, trustone, bone, antler, to name some of the bands I have used. All adhere well with the method described.
Larry