Puron digital monitor
Following the wonderful instructions above from kinmanc and The Worm, I too installed a Mini3LV Puron system. I did just exactly what was described above, with two mods. My middle sensor is mounted to the bottom side of my hitch receiver, and I have the digital monitor mounted on top of my rear-view mirror.
I wanted the monitor above rather than below the mirror because I've very jealous of my window space. I was unwilling to cede the 3/4 inch below the mirror to the gadget.
I used self-adhesive velcro to mount the monitor to the mirror. While the included mounting gadget was ingenious, it also was very delicate. More important, it would not produce a good fit in the tight space above the mirror. It probably would be fine for mounting the monitor below the mirror.
I am delighted to say that after installing everything, the Puron device worked the first time, every time. I'm thrilled!
Here's a picture of the digital monitor taken while my 'X was parked inside my garage. The monitor shows 1.1 because I pulled forward enough to leave about a foot's space behind the car. (In my usual parking position, the monitor registers 'HIT' due to the sub 6-inch clearance.)
FWIW, the odd white object behind and to the right of the Puron digital monitor is my FasTrack transponder, allowing me to breeze through the toll gates at the many Bay Area bridges without stopping.