Fender washer to match the diameter of your hole saw
Long staples for heavy duty stapler, around 3/4"
Brads slightly shorter than your wood is thick
Drill with bits: 5/16, 19/64, 3/16
Sand it smooth.
Mark around the hole with a penny, and a diameter line for placement of the staples later.
Decide on the height of your bayblade and cut the 5/16 dowel to that length.
Pound it into the wood circle from the bottom, so that it is flush with the top.
Drill two small holes for brads. (Those two steps not shown.)
Slip the washer over the dowel (on the bottom of the wood circle).
Pound in two brads to hold it in place. It can also be hot glued into place, but will eventually fall off in the heat of action.
Put two or three fender washers if you think it will make your bayblade more lethal.
If the staples go in too deep, pry them back out with a flat blade screwdriver. Short staples won't cut it - they'll need to be sticking up about a 1/4 inch, and sunk in as deep as possible.
File your performance tip to the shape of your choice, ruthless, efficient, deadly.
Since it's more massive, it will have more momentum, but also may cause the launcher to skip some teeth and eventually screw up as it accelerates it into action. Go easy. We're still working on a homemade launcher.
File the tip to a different shape for different action. Flat tips tend to travel, curved or pointy tips tend to stay put.
File grooves or build up texture with hot glue if you think these will give advantage.
Tall bayblades' shaft will contact the commercial ones' edge - a distinct advantage. If you try to stop a spinning object (your miserable opponents' b-blade) by touching it at a large radius, you'll be able to exert more force (torque) to slow it down. It, on the other hand, will be touching your (highly superior) b-blade at only the radius of the shaft, thus having far less torque to slow yours down. Resistance is futile.
A long spin is determined by many factors: mass, radius, air resistance (smoothness), balance, friction with the ground, collisions, and more. In the area of balance, the commercial ones have a slight advantage - the machine that spit them out likely made them perfectly balanced. You will need to optimize all the other factors to achieve victory, and that you will surly do.