Two Balancing Bats, one smaller and one larger, is another, yet simpler, venture into the Autodesk Fusion 360 feature "Center of Mass" calculation.
This design is quite simple; print either or both bats at 100% infill, and the cone at 20% infill. Place the indent located at the bottom of either bat on the cone, and give it a spin. It is important to print the bats at 100% infill in order to maintain the correct center of mass (at anything less than 100% infill, your slicer infill pattern, as well as mine, is more than likely not balanced).
I've included all files, including the Autodesk Fusion 360 file "Two Balancing Bats v1.f3d" that illustrates the steps I took to design Two Balancing Bats.
As usual, I probably forgot a file or two or who knows what else, so if you have any questions, please do not hesitate to ask as I do make mistakes in plenty.
Designed using Autodesk Fusion 360, sliced using Cura 2.5, and printed in PLA on an Ultimaker 2+ Extended and an Ultimaker 3 Extended.