Based on your recommendations, I ordered the rails and carriages from Fred at BST - excellent communication, great pricing and quick turnaround. Time from payment to delivery was 8 days (paid Sunday evening, received Tuesday the following week).

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I'm going to test bolt things together this weekend to measure up various bits and pieces and see how she slides. I'm going to get someone local to machine a few bits of aluminium for the extra bracing on the gantry. Do you guys lubricate the carriages before putting them into operation? They feel like they're a little 'dry' out of the box, but not sure if that's the ZA preload I'm feeling?

Now it's down to selecting the ballscrew for the X axis. Some folks on a Dutch forum suggested going for dual ball screw to prevent the gantry from racking. Gantry width is 800mm, and as mentioned I plan to mount a 2.2kw Teknomotor spindle. This machine was originally designed with steppers in mind. Will adding servos (with their potential for greater acceleration/rapids) make a duals screw with individual drive a more stable solution? If so, 2020 or 2010 for both, or downsize to 16mm screws?

Also, is there any significant upside to getting a C5 ground ballscrew (e.g. a TBI from Tuli) vs a C7 screw from Fred here?