Distance for the rails on the gantry make sure you get the maximum distance feasible as that way you reduce the moment applied due to cutting forces axially against them. So say for instance at the very edge of the gantry plate or even better on the top/bottom and that way you get an even larger distance to reduce the moment.

The 2.2kw WC spindles are really good, mine is super quiet. The water pump creates more noise on idle!

Rob