I will attest, this works perfectly. I do remember doing this years ago and totally forgot about it Well done!!!
There is one thing I need to add. I was not able to access iCloud. It seems that access to iCloud is based on your smbios. If Apple thinks you have an older Mac, it might deny you access to iCloud. There is a simple work-around.
Get Chameleon Wizard and just change the serial number. You do that in the left side column. Start Chameon Wizard, SMBIOS->Edit then select the circular arrow on the left (next to the word 'select') Next click on both 'Randon' boxes and then click on 'Copy'. Save the file. You might need to reboot and done. You should now access iCloud