Chris - thanks for your usual well informed information.

I looked up the Autofarm system. It got me to thinking perhaps the stock conical cup washers could be machined to allow a thin O ring to be captured by them. But it looks like there isn't much to work with there. For what they are, the Autofarm does seem a bit expensive.

Did they omit provision for a hex wrench to engage the nut end?

I also believe that the nuts may be Aluminium which would limit the preload and it doesn't look as if there is a provision for the hex wrench which does concern me as I can see them being tricky to remove.