Hi! I've installed both of those on a previous car, and had to play a bit with the proximity sensor to get it right... Connect it and run it loose with it's wires and see what kind of results you get. Generally speaking it should go as near as possible near the center of the car, but for the best results you'll have to test it in various locations and angles in the NSX to see what works, then adjust the sensitivity.
Shock sensor: should be on something as rigid as possible. I'd avoid the door simply because it's a pain to run wires into it if you don't have to. Again, if it has a sensitivity adjustment, you can clamp it somewhere or hold it tight against the test surface while someone else activates your alarm, then kicks the tires, slaps a window, etc. to see what works best for you.
Don in Heidelberg