It turned out that there is no need for a custom front axle as OEM Kawasaki ZX-6R front axle is the same diameter as Harley-Davidson Sportster.
I have not been happy with prototype wheel spacers. Neither appearance, nor manufacturing process. So they have been updated to make them visually more appealing.
The same goes for front brake rotor adapters. Now they will match the design of all other components better.