Hi Steve,
The first photo shows the two joined trusses. On the side you can't see, I drilled a small hole through the bolt and placed a pin in it to hold everything together. The aluminium block is tapped to accept the bolt. The first few millimetres are drilled with a wider hole to accommodate the pin. It's a very crude attempt to do what is shown here:
http://www.wcc.net/~myastronomy/ATM/B3/Upper%20Cage_truss%20tubes.htm
As I have built it at this stage, collimation does not hold between setups so the idea needs some work. It is however very rigid.
Hope this gives you some ideas.
Rod.