On 27 Apr 2023, at 20:51, Chuck Church <chuckchurch@gmail.com> wrote:

  Is there a ‘standard’ distance between front and back rails that devices usually adhere to?  

There isn’t a standard for rack depth, AFAIK, but one typically sees anywhere from 27in/69cm – 50in/127cm, in my experience.  42in/106.7cm & 48in/122cm are quite common depth dimensions.

Others here may have more specific information.