Secondary cage, side view
This drawing shows the dimensions of the truss and spider mounting points. The T-nut for the truss clamp screw is not shown, but should be centered between the mounting points. These mounting points are M4 hexnuts, which are 6.5mm accross and thus fit nicely inside the 10x10x1.25mm truss U-profiles. Note the offset of the hole for the spider screw, the height of this screw depends on the thickness of the secondary mirror.
The trusses are sunk completely in the cage walls.