You want the cable to be as short as possible. And, thin sheet-metal, like the strut tower (white area pointed out) isn't the optimal ground (but works if no other options are available). Is there a bolt near/on the subframe that you can use to ground? Be sure to get your drill with wire brush wheel out, and shave away absolutely any anodizing or paint that may be on the surface that'll make contact with the connector end. If you live in a high humidity/salt area, or just to be sure, you should spray the area with a squirt of paint or battery terminal sealer AFTER you have the bolt and cable end tightened back down, too.