I installed a
SNM D12 today, using this trick. Worked quite nicely. I did take a few pics of the install process, which I will post up later.
I used the slightly heavier gauge (heavier than a coat hanger) wire which supports industrial / commercial drop ceilings. I cut two pieces, each about 6" long, and bent a loop into one end of each piece. Using a trial and error fitment technique, I adjusted the wire on the light's existing bracket mount to achieve the proper angle, and tightened the wire down with the light's bolts.
It took about half an hour to get the wire bent appropriately to snug the assembly to the headliner and to get the angle right so the LEDs were at maximum effectiveness. I did not pierce the headliner, but rather wedged the wire between the headliner and the steel roof of the car.
Depending on how snug you make it, the wire may be all that is required to hold the light in place. In my case, the wire was about 95% in this regard, there was still a very tiny amount of movement which aggravated me. I ended up using the rearview mirror to kind of assist in the holding up of the light. The mirror offering support from the bottom and the wire offering support from the top secured the light 100%.
Tools used were a hacksaw to cut the wire and a bastard file to flatten the sides of the loops, so the light's screws would better grip the wire loop. If you were going to pierce the headliner with the wire, the bastard file would also be useful for grinding down the end of the wire into a IV catheter-like point.
I'm quite pleased. The light is higher on the headliner than it would be using the OEM suction cup mount, and looks more "permanently professional". There is a small bit of wire exposed between the headliner and the light, but it is only visible from the interior and the photos make it look more noticeable than it really is. I'm pretty anal about neatness and symmetry in my installations, and it does not bother me, so it should be okay for other people, too.