Aluminium CNC log.

[Jonathan]

how is this for Z and y?

I think you should go for the wider aluminium. It's annoying, but it won't hurt to have the Z axis a bit wider/stronger. It looks like you're using the same aluminium for Z... I'd make it stronger by putting the linear rails on the bit that moves up and down and the bearing blocks on the piece fixed to the gantry. That also saves a bit of aluminium/weight.

The stepper motor mounts have poor torsional stiffness...I'd either use bigger bar or plate or something.

Looks suspiciously like my spindle mount in the drawing :)

no snide remarks about it floating! :)

Wingardium leviosa.