So I got the additional hardware I needed from Anzor and have subsequently completed construction of the main frame. It's now looking like this:
Which is awesome. The great thing about the design is how easy it is to assemble and swap parts in and out. I realised that for the way I am going to build the y-axis I needed a couple of extra t-slot nuts in the lower ends of the frame. So you simply unscrew the particular aluminium extrusion and slide it out. No need to disassemble the whole rig or anything.
I'm stoked with my colour choice as well. It cost $25USD extra to get the aluminium in black, but I think black with the sky-blue PLA looks really awesome.
Since I took the above picture I've attached part of the y belt tensioner and the y-axis motor mount.
I've been talking to James about the y-axis carriage and I think I'll go the same route as him. Hardwood with 4 PLA holsters (one for each bushing) cable-tied, or similar to the hardwood. This seems like the simplest way of constructing it. Maybe later I can look at a printed carriage or something, but at the moment my main goal is to get the printer up and running, optimisation can come later :-)
James is currently printing the z-axis components that I need to continue construction. I'm also getting him to print the y-axis rod supports as well. Will get him to print the wade's extruder components later on.