@Jacktax if you can link me to the page with those instructions about the DCN, I'll see if I can get that page removed, its several years outdated.
The issues you may find when Efiling from multiple computers
Your EFIN is only good for Efiling from one address, so if you're Efiling from 2 different offices, your EFIN is only good in one of them, youd need to apply for a second EFIN for the second address (super fast turnaround for additional EFIN requests).
Receiving acknowledgements may get goofy, you wont be able to pick and choose which acks to retrieve,once an ack is received on one system it wont show up on the second, you end up having to highlight the pending returns and use Update Acks of Selected Returns if the Ack has already been received on the first computer.
Hope this helps!