Front railed body with switch housing

I don't work with STEP files so I don't have those.  I added the OBJ for the switch housing.  
 

SMD switch for volt checker:

3x6x4.3 or 3x6x5mm 

Rocker switch for power on:

8.5x14mm for the thinner section and the wider part is 15x10.5.  You can also just take the measurements from the OBJ or the STL.

volt display:

22.5 × 10 × 7mm (length x width x height)

I used m2x4mm screws to secure it

I soldered the positive from power lead (xt60) to switch and that positive to gearbox.

positive from the xt60 to the pushbutton and from there to the voltmeter.

negative from xt60 to gearbox AND parallel to the voltmeter.

I also put 2mm bullet connectors between all this and the gearbox in case I want to just skip the power button entirely I can just put an xt60 on it without having to resolder anything.

If you don't know how to do this part I'd skip it and not risk anything.