Hi again,
Just figured out how to "PDF" some cad files so I'll post a couple of these to give an idea of how the design evolved.
The Gantryplt file shows how a pocket was formed to accept the end of a piece of Bosch 45 x 45 ali profile. The Step Four cut this out along with the other holes and the outline and it was a perfect fit over the ends of the profile. A 10mm threaded rod down the middle hold it totally rigid.
The second file shows an end view of the various bits drawn together. It's not quite the same as the finished item as I made some last minute changes, mainly on the overall height. Hopefully this will make the earlier pictures a bit easier to understand.
Cheers
Nick