Using Chassis as a conductor for DC Power Supply Return
I would think not.

For one, if either device was removed from the chassis (by the unwary) for fault diagnosis then the operation would fail and damage may result.







simulate this circuit &ndash; Schematic created using CircuitLab

Figure 1. (a) What you've got. (b) Standard wiring practice with ground at one point. (c) Ground at two points and 0 V line connection.

Grounding at both devices as in (c) risks ground loops which are problematic in low-voltage signal circuits. In your case with both devices on the same chassis it might not be a problem.