I am picky about sight lines, clutter and wires in my vehicles....which makes using a portable gps a bit of a pain. I am very pleased with my solution and I have had a number of people say "thats a great place for the gps".
* Does not block windshield at all
* Is not obvious from outside (theft)
* No visible wires
* No dedicated plug into power outlet
* Switched power (vehicle on, GPS on...off...gps off)
* Easy to glance at while driving
* Easy to reach and hit buttons
* Does not block air from Heat/Cooling
* Work with hard and soft top.
I cut a bit of cardboard the size of my wide screen nuvi and kept it in the car for a while trying different places. I think my final spot is about perfect as it takes advantage of dead space above the rear view mirror.
Notes: The mount arm I used is from an older nuvi and there is a pivot on the arm between the suction cup and arm. This is key for the mount point. Nuvi's with the flip out antennae may not work. The only downside is that you can't do the upside down mirror mod. Standard power adapter routed in the trim down to the void on the right side of the dash. Tapped into the switched power of the left power outlet and a cig lighter extension routed to meet the power adapter and joined in that right side void (very easy routing with the glove box out. Easy to remove all the stock gps parts,