The wooden support board is carefully cut to be the same height as the inside of the sled, and mounted solidly so that it does not move. Then the keeper tab is removed from the ethernet plug and it's inserted into the player. Then the player is inserted into the sled with the ethernet plug still in it. Then the glue is applied to the plug to glue it to the support board with the player in place. The glue is allowed to dry/harden with the player in place. After the glue is dry, the player is pulled out, leaving the plug mounted in the perfect position. Additional glue can be applied to further support the plug at this point.

I went a little further and beveled the vertices of the plug with 45-degree trims so that it would dock even easier (just in case it was a fraction of a millimeter off center).

After all is said and done, the player should slide in and out of the sled and the ethernet should dock perfectly every time.