the strut tower is a fairly structural point, which makes it a good spot.

My 05 has 95k w/ 75k spent on michigans salt roads and the last 20k spent in salt air on the beach. No corosion left.

Sand down your grounding point, bolt it down, and paint it up to seal it. You shouldn't have to worry about rust. it took me a healthy bit of sanding just to get to metal on mine.