Then weld flange nuts to the fender washers (?).Mostly because I wanted to see if I could make fender washers work there. I even picked up some when I got the rest of the hardware, but unfortunately they won’t work unless I cut quite a bit off. They’d have to be more oval than round to fit in behind the flanges. Which isn’t entirely out of the question yet either.
Also, I was going for the largest possible footprint for the nuts to distribute the load as much as possible (hence the fender washers) and while strong, flange nuts typically don’t have that large of a footprint to them. They’re easy enough to get for 1/4” bolts, but much more difficult for the machine screw sizes like the 6-32 I’m using for the upper flanges.