Sorry for the delay in replying. Had ISP issues for a few days and my posts seem to intermittently require moderator approval (though I think it's when the post includes links).

Jonathan: I think I'll be looking at some kind of pocket, but I still haven't started to research the pulley systems yet so I don't know what I will need in terms of size and clearance.

AdCNC: Awesome build. This axis isn't fixed to the main structure though, it will be the X axis unit mounted on the Y axis.