Here is a picture of my WattsLeft™ mounted up by the Rear View Mirror.
Privously I had used a metal hook to hold it in place. But now I use just the Industrial Strength Velcro I currently ship with WattsLeft™ units. But instead of placing it on the bottom and mounting it to the dash I just put it on the top and mount it to the head liner.
If you are going to try this I recommend first attaching just the hook side of the Velcro without the WattsLeft™ attached. Attach just the loop side to the WattsLeft™ by it self. Let both sit for 24 hours to let the glue set. After 24 hours you can attach the WattsLeft™ to the head liner. Of course you need to route the cable up inside the left side pillar and inside across the head liner.
If you want to remove the WattsLeft™ don't just pull it off. Use your finger between the two strips of Velcro and slide your finger back and forth unlocking the hooks and loops til the Velcro is fully released.
I can post more pictures if people are interested.
In this position the WattsLeft™ box can not be easily seen from out side the car and it is shielded from the sun by the dot pattern on the glass.