If you look on the x-ray you will see that toward the front of the USB port there is nothing, not even ground plane under the PCB. I would try to at least shine light or laser through to confirm (copper is opaque bare PCB should be somewhat translucent) but two holes drilled on either side and a loop of copper or copper clad steel looped and twisted underneath, locking the twist with solder should really anchor the port down well especially if it is soldered to the top of the port.