I just watched your part three on the Ferris wheel. I left a comment but don't know how quickly you'll see it.
If you use your threaded rod on ALL of the spokes it will stiffen up better. If you use larger rod, say 3/8" or 1/2", it will be even better. Using the rod will make it easier and better for take down and assembly. I would also suggest you put the nylock nuts on the INSIDE so as to pre set the depth the rods fit. As you said, make them all the same so as to reduce assembly problems. You could use the nylock nuts on both sides and eliminate the lock washer. I suggest you use the thickest washers or double up on the washers to make the bearing surface larger and thus reduce the flexing even more.
It's looking real good. Keep up the good work. If you want, we can communicate through email. Just let me know.