I just picked up a RDLOGICS 1/12 arbor:
When mounting the front wheel in this arbor, it only centers the wheel on one side. The other side just applies flat pressure.
The RC4LESS arbor seems to do the same thing:
Again, you'll notice the flanges are only on one side. Is this normal with all 1/12th arbors? Why in the world wouldn't they have flanges on both sides?