Agreed Scott there is no FAA reg, but on the other hand, why not use all the strength that soft aluminum fork can provide? There is ample room on the backside of the fork from the tire when threads make it through. I choose using a thin-washer and a split lock washer (not per plans), the latter just a personal preference in this type of application. With the thin flat washer/split lock washer the stock bolt was short and I should have been pro-active in replacing, instead I did so in the repair mode, my bad.
Dues paid 2017
RV7 built & sold, 500h of pure joy in the air: sold
RV10 slow build & flying & loving it