Although I haven't said anything for a while, its not to say i've been idle, rather the opposite, between real life, work, a robotics competition etc, i've only just got back into it again.
So I mounted the partly built Z axis, and found a major issue, forcing a redesign of this.
So I sketched up an idea, using 608 bearings
And made a mockup of it.
Then I went back to working on finishing the Z axis. I made up two blocks, 1 threaded drive block, the other a guide block, and no matter what I did, I got binding, so I am still working on this, even today.
The photo shows the severe misalignment contributing to the bidinding issue, also I have to get new blocks made.
To the right of the photo is another view of the mockup of the linear bearing for the Y axis, working on this at the same time as the Z, and using the suggestions people have made, I am now making them.
I am still not happy with the bending I had done in the mockup, so before I do this for real, I reckon aother test is in order.