I've built this machine 100 different times in my head!!!

[JoeHarris]

I remember being advised that it was better to keep the ballscrew as close to the z axis as possible - between two ali extrusions rather than behind one...This is maybe not such an issue with profiled rail? I like how compact this is but does it come at a price?

[Jonathan]

I remember being advised that it was better to keep the ballscrew as close to the z axis as possible - between two ali extrusions rather than behind one...This is maybe not such an issue with profiled rail?

That's something I mention quite regularly. Profile rails will help to compensate for the ballscrew not being in the optimal location, which is directly between the rails on the gantry, but it will still be better if the ballscrew is closer. Currently the ballnuts seem to be 'out on a limb' which risks the plates they are mounted on bending which is best avoided.