Steve, I can see why you use hard washers -- actually seems like a good idea especially if the tailwheel is going to get some (a few) shock loads around the yield strength. But if someone out there puts a washer under the head, make sure it clears the radius on the head.
I just talked to Wup, appreciate his offer to take these parts back. I will package up mine & Randy's.
I have ordered some AN8-21 bolts. After 35 years at Caterpillar where the smallest bolt is 3/8 diameter, I feel qualified to overdesign this sucker!