I'm also using a tc1100, a cheaper (less expensive might be the right term) alternative may be using a dock you can find them on e-bay for about $25 they are heavy so shipping won't be cheap....I took one apart and I am going to try and drill some lightening holes in the metal base before I mount it in my truck the advantages would be
2. 4 usb ports that you can leave hooked up to the car
3. power supplied to charge the tc1100
4. mic and headphone out to your radio
5. automatic swithing from portrait to landscape when the tablet is rotated
6. a slot for a disc drive...
1. mount will take a little more work
2. 2D hinge will make alingnment with the user less flexible but I think you can figure out how to change alingment if that is an issue for you
another option on the hinge would be to extend the cable between the mount and the base and use a suction cup attached to the mount off a ball and socket...Just thinking out loud, good luck and keep us posted on your install!