I don't have any experience with those lights, but I can't imagine it would matter either way.
You could put all the grounds together and connect them to engine ground instead of the SPod ground, but still land the positive wires from the lights on the SPod positive terminal (for the particular switch circuit you want to use) and the SPod would still switch the lights on and off.
I can't imagine the lights would fail if they were grounded through the SPod though. How many lights are you using, and how many watts each are they (I assume 100W, correct)? Will they all be on the same SPod circuit/switch?
Last edited by BigTB; 03-10-2015 at 02:56 PM.