I made a custom mount for my Seidio car dock for the original Droid so I wouldn't have to have it attached to the windshield or dash and wanted to do the same for my Droid X. Since Seidio hasn't released a dock yet, I got the Motorola dock and had to change it up a bit. In the end, it turned out better than before.
Left over from before, I tapped in to the stereo power harness to add a cigarette lighter adapter and plugged a 2-port USB car charger in to it. One runs to my Blackberry Bluetooth adapter and the other to my Droid X.
I used half of the Motorola car dock mount and just bolted it directly to the side of the cubby hole above my single-DIN stereo. I used a crown lock washer between the mount and the cubby hole side to increase the friction vertically. The articulating ball mount is in tact as it was originally.
I'm also using Settings Profile ($1.99 I think in the market) to automatically set brightness to auto, calls to speakerphone, media volume to max, and open Pandora. (I also disabled the car dock app) I get in and put the phone in the dock and it automatically connects to my BT adapter and starts playing music. Pretty happy with the setup.