In the early '90s I did development work on a Tony Foale centre hub bike, built around a Yamaha RD350LC engine. It was a Parker type front end similar to a Yamaha GTS1000. No pics, sadly.
The Mead and Tomkinson endurance race bikes (powered by Kawasaki 1000 fours) were an interesting development from the Difazio. Instead of a kingpin inside the front hub, there is a ball joint. The side carriers for the brake calipers of a Difazio become part of the suspension, with a ball joint at the top and an upper wishbone above the tyre. It greatly lowers the stress on the lower wishbone, and give more consistent steering rake. If I remember correctly, Difazios have way too much trail, the M+T system cures that.