It seems a bit overkill for just a 7" tablet. I have tried a few setups and have been happiest working from 1" pipe to RAM mounts. RAM has a variety of modular attachments to secure to your dash or floor, and some great tablet mounts. I have a molded mount made for my older itronix tablet and an X-Grip III for the new 10" tablet. The X-Grips hold things very firmly. In addition I pick and choose between cradles for phone, GPS, a belt clip for an extra 2m radio, and even a self leveling cup holder.
My first attempt was a floor-based "tree," but that got busy and eventually I got tired of it being in the way. So far the solution has been some sch40 pipe I bent up and bolted to either side of the dash, allowing any combination and placement of the various mounts in exactly the location I want. It is probably overkill for most, but for more than a couple devices it works awesome. A friend of mine did a similar 1'-2' wide bar in the center of his Vanagon's dash further toward the windshield, using u-bolt ball mounts like I do.
You can really crank the ball mount arms down and they don't move. I use bushings against the dash pad in the wagon to keep vibrations minimal, and in the FJ40 it is a welded bar between roll cage supports.
My advice is to keep your base bar length as short as possible and come up with a very secure attachment to minimize vibration. Most of the ball-attached arms I use now are under 6". RAM's suction mount is very strong and I've run it in my pickup with the heavier Itronix tablet attached over rough roads without anything close to falling. That or even a screw-on mount somewhere on the dash would work well for a single device.
version 1 with a growing tree of devices and early tablet. it moved quite a bit until i wedged a mount arm against the dash.
dash bar with everything tossed on for demonstration. keep in mind all the attached things can be nearly infinitely adjusted and moved across the width of the dash.
another view, a bit more sane. 2m radio head uses a ball mount bolted to rear view mirror mount bolts
bar with an unused ball mount and the phone cradle at the far end. This setup also makes it easy to remove things and stow quickly.
I usually order stuff from gpscity.com, but I think you can also buy direct from RAM. They have pages of mount hardware to go through.
