Here you can see a riser. Click the picture for a bigger version -- it is
easier to see what is going on. The bottom of the riser is connected to
a vertex in the top dome pentagon. I built my dome with the bolts in
these verticies pointing "out" so I could attach the right angle brackets
without disassembling the vertex.
You can see that the angle-bracket at the base of the riser is arranged so that the riser can rotate with respect to the angle-bracket. The angle bracket itself is in the same plane as the vertex, but the riser is free to point vertically. Use a 1" bolt to attach the riser to the bracket at the bottom and top.
You can also see that the angle-bracket at the top is is arranged so that the second bolt goes straight up. Use a 2" bolt pointing up.