The Rosso twins are
Join Date: Oct 2011
Location: United Kingdom
County: Tyne and Wear
Yeah never thought of that, just looked at you pic earlier which showed it, doh!
Think I would go the higher position personally, I fitted some to a Vw transporter a couple of years back and because it was quite a low bumper if you reversed up a hill it just screeched as it could detect the road rising behind it, and also picked up low kerbs etc.
The other thing I would say is move the outer two sensors right onto the corners (if you look at factory fitted ones they are all right out) as it gives a wider span in case something is just at the corner of the car, the middle two will cover directly behind.
Good luck with it.