If you want to expand the 5" guard box on your network bay, the following options are available from Telect:
P/N 02199-12 : 3" extension for 19" Network Bays, includes a 8" cover
P/N 02199-11 : 3" extension for 23" Network Bays, includes a 8" cover
P/N 02199-13 : 5" extension for 23" Network Bays, includes a 10" cover
P/N 02199-20 : 7" extension for 23" Network Bays, includes a 12" cover
These extensions can be bolted onto each other to for larger sizes, if needed but would not include a one piece cover.