From VEX Wiki

Mounting a new VEXnet Field Controller to an old (purchased before Sept. 2009) VEX Field?

The VEXnet Driver Interface circuit board found in the VEXnet Field Controller & VEXnet Field Upgrade Kit does NOT mount to the controller "post" found in the VEX Competition Field Perimeter Kit. The holes in the side of the post are designed for the old VEX Field Controller, and are not correctly aligned with the cable ports on the new VEXnet Driver Interface.

There are several simple options to make this work:

1. Purchase new Field Control Posts which are compatible with the new System.

2. Mount the Driver Interface on the back-side of the post (outside the C-Channel) facing the field.

3. Modify your field control post so the cables can pass through to the Driver Interface.

4. Mount the Driver Interface using standard VEX Standoffs and Screws such that it mounts "above" the flange of the control post, and the cables can be plugged in.