I am not a steering guy at all, let alone an experienced one, so feel free to laugh heartily at my folly (and perhaps point me in the right direction), but wouldn't a 'backwards' caster angle like the one shown create inherent instability? I look at it and imagine that everytime the contact patch moves 'forwards' the tyre would try to turn around on itself (as a typical caster wheel does).
Definitely agree with the scariness of the toe base...