All my drill bits are dull, so I couldn't drill the last two holes in the top bracket. I'll have to get another set. This is as far as I got today:
Ah, those springs are so neat, curling around the fixing bolts like thatThis shows the 4 springs mounted. The loops on each end of each spring are just the right size to fit over the bolts. That will keep them in place. The holes in the bottom plate and top bracket are 1/4", just enough room for the bolts to pass through, so that will help in stability also. The locknuts on top determine how much tension is on the springs. As they are tightened, it will bring the fork end upward and change the geometry of the wheel somewhat.
I'll trim the bottom plate to look better. I will also keep the fork legs curved, straightening them won't really make much difference and might make them weaker. I'll design the bottom flanges next.