Ground connections

I am using a maxflex and was wondering if I can use the housing as the ground connection? Basically I have a light housing on either side of this mount... http://www.chainreactioncycles.com/Models.aspx?ModelID=12871
The switch is on one side and the power in and driver is in the other.

To get power and the switch cables from one side of the light to the other, I have had to carefully drill out my mounting bolts. I have only managed to get a 3mm drill though so can only pass the positive power wire and the positive wire for the switch through.

I know the ground is common on the board, but will this bring up any problems? The resistance is about 1-2 ohm.

Thanks everyone!