I am in the middle of using my old DX dock and an extra Razr dock to make one dock. Both docks come apart pretty easily. The USB plug that is originally in the DX dock simply pops out of the unit. You can then take the board and wires out of the Razr dock and using the cord that you removed from the X dock, you can use it to plug into the board from the Razr dock and use it as an extension cable back to the back of the X dock. Now take the board from the Razr and it fits snugly, without any modifications, to the inside of the X dock. I was able to just push it in place and friction will hold it in place.
This is the point I am at right now. Next I will have to drill a hole in the side of the X dock for the wires to come out from the Razr circuit board. After that I will cut the back of the Razr dock where the USB slider is, down so that it will line up with the port on the Droid Maxx while it is in the dock. I will still have to come up with a way to attach the sliding mechanism from the Razr dock to the X dock, but once I do that than I will have a working dock, including the USB slider, for my Droid Maxx.
This is what it looks like so far. This is the back of the X dock with the circuit board and slider from the Razr dock inserted in it.
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I will probably not be til next weekend before I finish this project, but I won't have a need for it for another 2 weeks or so. That is when I will be activating my Maxx. I am currently using my X2 until it is updated. Supposedly, there is one coming. Before I sell the phone to my son, I want to make sure that it is working good.
This has been an interesting project so far. I only have about an hour into it right now. I can't see it taking more than another hour or two to finish. I am just slow on my projects. It is easy to start one, but hard to finish.