A very shallow Skiff for modular.

I use it for a PNW and Mutable Instruments modules, none is deeper than 30mm.

You can extrude the middle part in the slicer to get any length (width) you want.

One of the side panels (Part_B) can be outfitted with a small peace of standard (2.54) PCB to connect it with bus cables in case you use it as an expander.

If you don't want this or use it passive, just print Part_A twice, they are symmetrical.

Have fun.